OKAY I ENDED UP FINDING OUT ANOTHER ONE. So a quick guide with minimal spoilers for others:
One ending requires you to just... be mean to him. Don't pry into him, don't call out to him, be apathetic and avoid him. If you're having recurring dreams, that's GOOD
The other two endings, be NICE to him, and make sure to save at the part with the paintings, if your character has dreams, THAT'S BAD. Then there's just a simple branching choice, one is just "and they lived happily ever after" and another is "om nom nom" but happy
The fourth ending is just.. ask him bout the tombstone. then ask some more. and then more. and then say hello to the golden gates. Now just gotta figure out the fifth!