Sounds like my father and mother to me, or my aunt and uncle. They both (father and uncle) hated most things about life, lacked grace or gratitude, would verbally beat up my aunt and mother. My aunt, has taken it for over 25 years, and has done snarky rebellious things their entire relationship to combat it, "oh, you think I'm fat? I'm gonna starve to 103lbs at 6'0." and has now disabled herself. My mother on the other hand, fought back verbally and got very aggressive, became a master manipulator, divorced and continues to do adulterous acts.
Both the men and women were a mess, and I'm not claiming you are. Really, it sounds like you have been responsible and kind-hearted more often than not in this situation. However, I think this is a treacherous road you're going down on, very sick indeed. Both my father and uncle were very skinny, after starting out fat in the beginning. Constant odds against themselves, no room to breathe, poison in the silence, causes your immune system and nervous systems to fight back against themselves. In other words, you are killing your body and he is killing his by what he's doing. You seem to he getting the greatest food you can, and there is little that can do right now. There is little an independent priest can do, which is the greatest form of life aide and spiritual help you can get. Since it's downhill in terms of help from there, and you have resorted to an online forum, I don't blame you, but just like when I came on here after months of finding a pure, pious woman to court, some things take time or simply to abort more than anything else.
My father also had a problem with infertility, my mother never knew what it was, it took four, almost five years of trying for them to have me. I'm seeing the similarities adding up, I always regard that time in my parents' marriage as time for my mother to run away, although she couldn't until she became more insane.
All I can say for sure is he tricked you when courting, this is classic narcissism. Whether it's caused by childhood, or not having the nutrients he needed growing up, or as a chastisement to his parents from God, excuses aside this is narcissism.
I can say for sure now that your physical situation is getting better, he is near-incurable mentally. Perhaps he needs an exorcism from a priest, this is all I can recommend. Divorce is impossible and I truly hate that for you. I know you love him, you are wired to. It is a difficult situation indeed.
Hunker down, try your hardest to become celibate, tell him you're waiting for his procedure to be done. Don't wrestle with him, don't argue. I know how it feels to have no family, this is why I'm very particular in my courting process. You have selected wrong and I pray through God's grace you may recover physically and he may recover mentally for you both to have a fruitful life.
Have you asked him to truly make peace with, and forgive his mother and father? This has helped me tremendously, and everyone else I know.
If nothing which has been recommended by this thread works, it is him, most definitely, and keep yourself as safe as possible.