1) Correct, he’ll gain 6 points per day until healthy, or at least that’s what I have experienced.
2) He can play whenever you’d like him to play but there’s a small penalty (consensus is very small) when he’s not at 100.
3) Not really. If his durability is bad that increases his chances of re-injury but again, that’s a very small chance.
Important side note-If this is a freshman, juco, or transfer that has promises that need to be fulfilled he’ll expect those promises to be fulfilled once he hits 60% health, so you almost have no choice but to play him at 61%.