Question: couldn't we have someone, like, shank the bastard to keep it from fully healing and getting back up?

It's one round away from fully healed. Meaning it's almost fully healed.

What do you think attacking a sleeping monster is going to do?

Edit: Answer: It will wake up and be angry.

Option B: spear it through the head.

Sleeping monsters ain't got no evasion.

They still have HPs and ARM, though!

How about an eye, would an eye work?

Or a nostril, all the way to the brain.

Its brain is very small.

Edit: And its skull very thick... and the head is one of the parts they wanted in good condition.

Well a spear up the nostril should still fuck SOME shit up.

Maybe it'll end up trying to eat its own arm.

It will inhale your spear like cocaine and go on a drug induced frenzy.

... But a fun drug-induced frenzy, right?

That thing is just asking to get devoured.