While it's a clever idea, there is no way to mitigate damage from lightning lure. There is either damage delivered or no damage delivered.
Damage or no damage, there is no in between
Lightning lure does give you some control in how far you pull it, but it's either going to end up within 5' (and take the damage), or it will not end up in 5' of you and still be up and able to act on it's turn.
Some attacks can reduce a creature to unconscious rather than death
There is a rule for knocking a creature out, but that doesn't apply here because it's only for melee attacks and this is a strength save not a melee attack.
Sometimes an attacker wants to incapacitate a foe, rather than deal a killing blow. When an attacker reduces a creature to 0 hit points with a melee attack, the attacker can knock the creature out. The attacker can make this choice the instant the damage is dealt. The creature falls unconscious and is stable.
NPC Death Saves?
Another consideration is whether or not your DM has NPCs make death saves. If they do, then this gives some time to stabilize the monster, but it also means you need to make sure NPCs actually die whenever you fight them.
Most DMs have a monster die the instant it drops to 0 hit points, rather than having it fall unconscious and make death saving throws.
Mighty villains and special nonplayer characters are common exceptions; the DM might have them fall unconscious and follow the same rules as player characters.
If they do decide to go the NPC death save route, they will need to make sure to communicate when they are or aren't doing prior so you aren't left 'surprised' when an NPC gets back up.
As an anecdote, we once had our DM not 'kill' a downed NPC. It had never happened before and it never happened again. And it was a really frustrating experience to learn that we hadn't killed him. If a DM is going to have some NPCs do death saves, that needs to be communicated to the players.