I was having everything make Critical Damage saves when they were hit and took damage.
Yes, once the Damage starts reducing STR, any creature must make a STR Save to avoid taking Critical Damage.
This resulted in the wolves and orcs (separate encounters) mostly leaving the combat due to failed Crit Damage roles vs being killed outright. Is this as intended? Is this normally played as “The orc slumps to the side mortally wounded” even if it may take up to an hour for death to occur unless aid is given?
Generally, player characters have little reason to keep fallen enemies from dying after the combat, so the default presupposition is that the fallen enemies are left to die or killed after the battle. If the characters want to take one as a prisoner, they can do so. This, of course, does not extend to non-living or un-living creatures. Reducing STR to 0 also kills the creature outright.