Having cancer doesn't automatically turn someone into a saint. My ex husband (not an a) had cancer for most of our marriage. It was one of the reasons I stayed so long. Guilt over his illness. What kind of heartless monster divorces someone with cancer? Blah blah blah.
He was still the same lying, bullying, selfish, irresponsible man whatever his health condition may have been. To the very end of his life he was manipulative and nasty to me, and he had remarried in a big hurry because he hated doing housework and taking care of kids. Don't let his illness be an excuse to keep you hooked, especially when it sounds like a lot of his health issues are either directly or indirectly caused by his drinking.