OP, I only really read your 2 posts in here. This guy & this whole situation sounds like a huge mess, so to me, it's not about fair or unfair. It's like you're tied down without even being married yet. I'd get out fast, without even feeling guilty about leaving him to pay the rent somehow. This is HIS mess & his responsibility, not yours.
You need to be the footloose & fancy-free 23 yo that you are & not wrapped up in this mess. Ay, ay, ay. I only feel sorry for his innocent kids in all this who have an incompetent, idiotic father who can't plan & think things out MUCH, MUCH, MUCH better than this. You mean to tell me he has not one relative to help him out with this?!