Oh, sweetie (hope my term of endearment doesn't upset you)...you CAN find peace. Really. You can. Anyone can. It can be hard work, but you can.
Okie, do you have a therapist or have you gone to Al-Anon? THERE IS PEACE OUT THERE.
If you haven't read "Codependent No More" by Melody Beattie, please start there then make an appointment and invest in yourself. Your son is already 44. He should have already launched. He has to do it himself and you deserve a happy rest-of-your-life. Your middle age son should not be controlling your moods AND should not be bankrupting you. Handing somebody free gifts does not make them learn how to succeed. They often just don't appreciate something they did not earn.
Please, please, please take care of yourself and your marriage. Since your son is already in his 40's, I feel your focus should be on your relationship with your beloved spouse now. I also feel he is trying to help you by giving you that ultimatum. He is indeed trying to be a rock and your best friend.
Hugs and more hugs.