Rei, after becoming the Weretiger, gets about 3-4 turns where he will only attack the enemy.
Turns after that increase the chances of him attacking teammates, then chances increases for him to attack himself, but normally fights don't last that long in BoF3, thanks to Ryu3.
Guts is a MP-free healing command that heals Ryu2 based off his current HP. The lower it is, the higher it heals.
At near critical HP, Ryu2 recovers to FULL.
Well, most people scale down boss HP due to the fact that you fight the bosses as a party, not as a solo PC.
Because rarely in a game that you do not need power leveling or some cheap trick to kill them solo. Except for a few overpowered instances.
Even then, most BoF bosses still have insane durability, and Ghaleon is still a bloody tank.
Also it depends on how much you respect Indy durability I guess. I respect G.Dragon's damage enough to kill before ToT activates, and Indy isn't killing Ryu2 before then.
Indy durability respect CAN get pretty........iffy between people's interpretations, but G.Dragon's horrible overkill is a fact most people have embedded into their brains.