First I am very sorry that you are going through all of this with your boyfriend. It sounds very stressful and you know we IBS'ers don't handle stress very well.
From reading your post I can tell you that it is NOT your fault. You are not responsible for his actions and he sounds like he is very unreasonable to me and controlling. You must do what is best for you and if moving out is the best thing then do it. You can't worry about his money issues.
Years ago I left my first husband after being married a couple of years. I told him that in 30 days I would be moving out and I have to say that 30 days was long and very uncomfortable. If you decide to leave I would give a short notice and go. You say you don't think he will let you leave, how will he stop you? Maybe it is best to just pack up and go without any notice.
Situations like this are made more difficult when you don't have someone you can talk to. I am glad that you have the supportive people on the boards.
I will be thinking about you and I wish you luck with your decision.