I was slowly turning him around. And it was working! Pussed out, gave up on him. Still feel bad about it. I might have saved him but for my lack of patience and moral courage.

Don't blame yourself, it really takes a lot of energy and it's not like you're obligated to do that anyway. Besides, it could've never work 100% thus putting you in a kind of co-dependent relationship. Good for you to abandon toxic environment, I think.