I recommend retaining counsel who specializes in this area. Per related past posts it's a bit of a gauntlet wherein if your DS DOR (drops on request) the obligation is likely on your DS, whereas if you are medically DQ'd you may or may not have an obligation. If you're injured while say completing PT with your unit, the cost or service obligation could be waived. But I'm concerned here that they may lump mental health into something outside of happening while participating. I'm always a little disappointed when a unit pushes to have the mid DOR and puts the obligation on them, when mental health is a concern - but see prior posts from others - it has happened.
I would say bottom line the health of your child is what's critical here, and if he ends up owing 2.5 years of scholarship back, it's challenging but at least you still have him, are getting him help, etc.
Sorry to hear your DS is struggling and glad you are getting him the care he needs. It's early in the semester - can he take a LOA and perhaps not have to pay for this semester at school, come home and say take 9 credits at an online school, continue his course of therapy, and then look to return if he's back on his feet? IDK, but maybe others can provide additional guidance on options. I would also call his adviser and the bursar's office for guidance - outside of ROTC, on his options for this semester and his path forward.
Good luck.