Good ending, reunites him with Carmen, who says "we never be apart again". Problem is, she's dead, so "reuniting" and "staying together thereafter", means...

Bad ending, hooks you up with Jordan... Who was done in by that pimp, before. But with or without her, Blackmore is an apparition, so it absorbing Torque, well...

Neutral ending seems to be a lot like "eternal conflict", or something.

Either way, Torque seems to be stuck in time and place, inside the ruined Garvey's children orphanage, with the facts/revelations that he had been a multiple personalities nutjob, who hired thugs that ruined his family, set up himself and his best buddy, etc. And credits screen is a tombstone saying RIP. Officially or not, is the protagonist put to rest? And was there or wasn't, a Suffering 3 rumored at one point, years ago?

Not at all. Tombstone in credits is like end of story, let it rest in peace... or not, everything that happens after is irrelevant because it's not part of game nor story.

Good/Carmen ending let's her watch over him, stay close always without distractions until they reunite in death. No one will stand between them now. Making peace with the past.

Neutral ending means that up to this point he still struggles with weakness and the past will still haunt fueling anger and what Blackmore is but there's still choice in everything he does, not easy shortcut option, kind of like balance.

Evil ending is basically opposite, Torque no longer exist, his personality, mind and the very essence is replaced, absorbed. Everyone but Jordan will still see Torque, she will see real mastermind. This is the only "death" ending but not in physical sense if you decided that he should just embrace it and let the past and old self die. Killing it is the only option to achieve this.