The first way is correct, as further evidenced by the introduction of the Artificer in Eberron: Rising from the Last War.
The optional artificer multiclassing rule for spell slots says:
Add half your levels (rounded up) in the artificer class to the appropriate levels from other classes to determine your available spell slots.
First, this confirms that at ...
High attack bonuses are possible
This is dependent on level and magic items. It is also dependent on the target's AC. A rather high modifier can be obtained with +6 proficiency, +5 dexterity, archery fighting style, a +3 bow, +3 ammunition, and ioun stone of mastery for a total of +20, making a attack roll result of at least 22 (a 1 misses anyway, vide Supra)...
With the introduction of the Artificer and the Battle Smith's Steel Defender, we now have precedent for a companion having HP equal its Con + your casting stat + 5 times your level, and the Steel Defender isn't breaking the game with its durability.
Regarding scaling toughness based on Con, almost every CR 1/4 beast has a Con modifier of +1, with a select ...
Can you command it otherwise? Yup.
We can see from your quote that if you command the beast (with some cajoling, perhaps; it does consume your action) to Attack/Dash/Disengage/Help, the animal will do so.
If you do not command the beast anything, it will Dodge.
What, then, if you command it other than Attack/Dash/Disengage/Help?
RAW: nothing special.
If you are asking whether you can tell your companion to do something besides a movement action for free, then the answer is no. Commanding your companion to do anything besides move costs you an action. Sometimes a DM will allow for something simple like, "keep your eye on him" , but if you plan on it acting, then you have to spend that action or ...
The text of the ability is:
At 11th level, you gain the ability to pass between the planes in a blink of an eye. When you use the Attack action, you can teleport up to 10 feet before each attack to an unoccupied space you can see.
and, yes, this means you can use the Attack action when you're not in melee range of an opponent, and then teleport to ...
A surprised creature remains surprised until the end of their turn on the first round of combat
How often during combat can you be Surprised?
What happens when your group is victim of a surprise attack but you can't be surprised?
Readying an action for sneak attacks in surprise rounds
What's the correct way to determine turn order in this ...
The creature remains surprised.
There aren't any special rules on the Dread Ambusher or Assassinate features that would cause a creature to stop being surprised. Since there aren't any special rules, the creature remains surprised until the end of their turn as normal.
If you aren't sure what the surprised state is, please refer to this question:
At which ...
There are a few potential concerns with this plan. Some of them work out in your favor, others do not.
Bonus action between attacks
You can take bonus actions between attacks, per the answer to this question.
Using both hunter's mark and zephyr strike
You can apply one spell to the first attack, and the second spell to the next attack. Of course, ...