I haven't returned to this game in a while, but I believe the different endings are based on three different stats, your relationship with Maisie, the main character's self image/confidence in their identity, and the amount of grudge they hold towards the family.
I did quickly check the code to find that Ending 3 might have way too specific of a requirement, so I'll change it and make it easier to get.
I'll put up a quickfix when I get home if that's okay, thank you for pointing this out!