If you take the disengage action, your movement doesn’t provoke opportunity attacks for the rest of the turn.

You used your bonus action on Flurry of Blows...

So you don't have a bonus action to hide at the end. Action Surge only grants an additional action, no extra bonus action.

On your turn, you can take one additional action on top of your regular [action and a possible bonus action] %read the brackets together%

You do, however, get a critical hit on every attack that you hit since the target is surprised until it's first turn in combat.

You can only Sneak Attack once (but all of your bow attacks qualify because Assassin gives you advantage):

If you take the Disengage action, your movement doesn’t provoke opportunity attacks for the rest of the turn.

You used your bonus action on Flurry of Blows...

So you don't have a bonus action to hide at the end. Action Surge only grants an additional action, no extra bonus action.

On your turn, you can take one additional action on top of your regular action and a possible bonus action

[emphasis mine; read the italicized portion as a single grouping]

You do, however, get a critical hit on every attack that you hit since the target is surprised until the end of its first turn in combat. From the description of surprise:

You can only Sneak Attack once per turn (but all of your bow attacks qualify as opportunities to use it because Assassin gives you advantage):

No

You only get 1 bonus action.

To do what you describe you need to use these Bonus Actions:

1. Flurry of Blows unarmed strikes
2. Dashing with Cunning Action
3. Hide with Cunning Action

To clear up some misconceptions:

The Disengage action doesn't give you extra movement

You seem to think that Drunken Technique gives you extra movement after you use Flurry of Blows but it only increases your speed by 10 feet. Disengage merely prevents opportunity attacks.

If you take the disengage action, your movement doesn’t provoke opportunity attacks for the rest of the turn.

To gain extra movement equal to your speed (70 feet after the Drunken Technique bonus) you need to take the Dash action.

Action Surge doesn't give you an extra bonus action

You used your bonus action on Flurry of Blows...

Immediately after you take the Attack action on your turn, you can spend 1 ki point to make two unarmed strikes as a bonus action

[emphasis mine]

So you don't have a bonus action to hide at the end. Action Surge only grants an additional action, no extra bonus action.

On your turn, you can take one additional action on top of your regular [action and a possible bonus action] %read the brackets together%

Automatic criticals?

You do, however, get a critical hit on every attack that you hit since the target is surprised until it's first turn in combat.

If you’re surprised, you can’t move or take an action on your first turn of the combat, and you can’t take a reaction until that turn ends

[emphasis mine]

Critical hits also double your Sneak Attack damage dice, so your Sneak Attack (whichever shortbow attack you apply it to) will do 4d6 damage, not 2d6.

You also have to go first or the target removes surprise before you get the chance to hit them (since it happens after their turn). There is no surprise round in 5e so the enemy rolls Initiative before your first turn (but gets no actions, reactions, or movement for that turn if they are surprised).

What you can do:

However, you can still get off your 5 attacks (and then some) with your build.

1. Attack action

• Shortbow attack
• Move into range (60 feet) for Extra Attack unarmed strike

2. Flurry of Blows

• 2 unarmed strikes
• Move away 10 feet with Disengage active (gained from Drunken Technique)

3. Action Surge: Attack action

• Shortbow attack (2 if you want because of Extra Attack)

4. All attacks are made with advantage and those that hit are critical hits since the target is surprised.

You just end up only 10 feet away and don't get to hide at the end.

You can only Sneak Attack once (but all of your attacks qualify because Assassin gives you advantage):

Once per turn, you can deal extra 1d6 damage to one creature you hit with an attack if you have advantage on the attack roll.

[emphasis mine]

No

You only get 1 bonus action.

To do what you describe you need to use these Bonus Actions:

1. Flurry of Blows unarmed strikes
2. Dashing with Cunning Action
3. Hide with Cunning Action

To clear up some misconceptions:

The Disengage action doesn't give you extra movement

You seem to think that Drunken Technique gives you extra movement after you use Flurry of Blows but it only increases your speed by 10 feet. Disengage merely prevents opportunity attacks.

If you take the disengage action, your movement doesn’t provoke opportunity attacks for the rest of the turn.

To gain extra movement equal to your speed (70 feet after the Drunken Technique bonus) you need to take the Dash action.

Action Surge doesn't give you an extra bonus action

You used your bonus action on Flurry of Blows...

Immediately after you take the Attack action on your turn, you can spend 1 ki point to make two unarmed strikes as a bonus action

[emphasis mine]

So you don't have a bonus action to hide at the end. Action Surge only grants an additional action, no extra bonus action.

On your turn, you can take one additional action on top of your regular [action and a possible bonus action] %read the brackets together%

Automatic criticals?

You do, however, get a critical hit on every attack that you hit since the target is surprised until it's first turn in combat.

If you’re surprised, you can’t move or take an action on your first turn of the combat, and you can’t take a reaction until that turn ends

[emphasis mine]

Critical hits also double your Sneak Attack damage dice, so your Sneak Attack (whichever shortbow attack you apply it to) will do 4d6 damage, not 2d6.

You also have to go first or the target removes surprise before you get the chance to hit them (since it happens after their turn). There is no surprise round in 5e so the enemy rolls Initiative before your first turn (but gets no actions, reactions, or movement for that turn if they are surprised).

What you can do:

However, you can still get off your 5 attacks (and then some) with your build.

1. Attack action

• Shortbow attack
• Move into range (60 feet) for Extra Attack unarmed strike

2. Flurry of Blows

• 2 unarmed strikes
• Move away 10 feet with Disengage active (gained from Drunken Technique)

3. Action Surge: Attack action

• Shortbow attack (2 if you want because of Extra Attack)

4. All attacks are made with advantage and those that hit are critical hits since the target is surprised.

You just end up only 10 feet away and don't get to hide at the end.

You can only Sneak Attack once (but all of your bow attacks qualify because Assassin gives you advantage):

Once per turn, you can deal extra 1d6 damage to one creature you hit with an attack if you have advantage on the attack roll.

[emphasis mine]

No

You only get 1 bonus action.

To do what you describe you need to use these Bonus Actions:

1. Flurry of Blows unarmed strikes
2. Dashing with Cunning Action
3. Hide with Cunning Action

To clear up some misconceptions:

The Disengage action doesn't give you extra movement

You seem to think that Drunken Technique gives you extra movement after you use Flurry of Blows but it doesn't. Disengage merely prevents opportunity attacks.

If you take the disengage action, your movement doesn’t provoke opportunity attacks for the rest of the turn.

To gain extra movement you need to take the Dash action.

Action Surge doesn't give you an extra bonus action

You used your bonus action on Flurry of Blows...

Immediately after you take the Attack action on your turn, you can spend 1 ki point to make two unarmed strikes as a bonus action

[emphasis mine]

So you don't have a bonus action to hide at the end. Action Surge only grants an additional action, no extra bonus action.

On your turn, you can take one additional action on top of your regular [action and a possible bonus action] %read the brackets together%

Automatic criticals?

You do, however, get a critical hit on every attack that you hit since the target is surprised until it's first turn in combat.

If you’re surprised, you can’t move or take an action on your first turn of the combat, and you can’t take a reaction until that turn ends

[emphasis mine]

Critical hits also double your Sneak Attack damage dice, so your Sneak Attack (whichever shortbow attack you apply it to) will do 4d6 damage, not 2d6.

You also have to go first or the target removes surprise before you get the chance to hit them (since it happens after their turn). There is no surprise round in 5e so the enemy rolls Initiative before your first turn (but gets no actions, reactions, or movement for that turn if they are surprised).

What you can do:

However, you can still get off your 5 attacks (and then some) with your build.

1. Attack action

• Shortbow attack
• Move into range (60 feet) for Extra Attack unarmed strike

2. Flurry of Blows

• 2 unarmed strikes
• Move away 10 feet with Disengage active (gained from Drunken Technique)

3. Action Surge: Attack action

• Shortbow attack (2 if you want because of Extra Attack)

4. All attacks are made with advantage and those that hit are critical hits since the target is surprised.

You just end up only 10 feet away and don't get to hide at the end.

You can only Sneak Attack once (but all of your attacks qualify because Assassin gives you advantage):

Once per turn, you can deal extra 1d6 damage to one creature you hit with an attack if you have advantage on the attack roll.

[emphasis mine]

No

You only get 1 bonus action.

To do what you describe you need to use these Bonus Actions:

1. Flurry of Blows unarmed strikes
2. Dashing with Cunning Action
3. Hide with Cunning Action

To clear up some misconceptions:

The Disengage action doesn't give you extra movement

You seem to think that Drunken Technique gives you extra movement after you use Flurry of Blows but it only increases your speed by 10 feet. Disengage merely prevents opportunity attacks.

If you take the disengage action, your movement doesn’t provoke opportunity attacks for the rest of the turn.

To gain extra movement equal to your speed (70 feet after the Drunken Technique bonus) you need to take the Dash action.

Action Surge doesn't give you an extra bonus action

You used your bonus action on Flurry of Blows...

Immediately after you take the Attack action on your turn, you can spend 1 ki point to make two unarmed strikes as a bonus action

[emphasis mine]

So you don't have a bonus action to hide at the end. Action Surge only grants an additional action, no extra bonus action.

On your turn, you can take one additional action on top of your regular [action and a possible bonus action] %read the brackets together%

Automatic criticals?

You do, however, get a critical hit on every attack that you hit since the target is surprised until it's first turn in combat.

If you’re surprised, you can’t move or take an action on your first turn of the combat, and you can’t take a reaction until that turn ends

[emphasis mine]

Critical hits also double your Sneak Attack damage dice, so your Sneak Attack (whichever shortbow attack you apply it to) will do 4d6 damage, not 2d6.

You also have to go first or the target removes surprise before you get the chance to hit them (since it happens after their turn). There is no surprise round in 5e so the enemy rolls Initiative before your first turn (but gets no actions, reactions, or movement for that turn if they are surprised).

What you can do:

However, you can still get off your 5 attacks (and then some) with your build.

1. Attack action

• Shortbow attack
• Move into range (60 feet) for Extra Attack unarmed strike

2. Flurry of Blows

• 2 unarmed strikes
• Move away 10 feet with Disengage active (gained from Drunken Technique)

3. Action Surge: Attack action

• Shortbow attack (2 if you want because of Extra Attack)

4. All attacks are made with advantage and those that hit are critical hits since the target is surprised.

You just end up only 10 feet away and don't get to hide at the end.

You can only Sneak Attack once (but all of your attacks qualify because Assassin gives you advantage):

Once per turn, you can deal extra 1d6 damage to one creature you hit with an attack if you have advantage on the attack roll.

[emphasis mine]