Hi and welcome.
I do some voluntary work helping others and something stressed throughout our training is that you have to look after yourself first and only then should you support someone else. It's sounds selfish and goes against the 'western way' but it's common sense (of which I have little!!).
Your partner is an adult. He chooses what he does, you don't do it to him. You mention your worry that if you leave him he won't survive. He is putting you on a guilt trip. Again, if he harms himself he took that decision.
He needs to face up to the fact he has a problem and acknowledge he needs to do something about it, and you can point things out to him until you're blue in the face but until he chooses to see this he won't think he has a problem or will blame everyone else.
But you do have control over what you do. And you have to do what's best for you. It's not selfish, it's survival.
Hark at me going on like I know what I'm talking about. If you feel I'm talking rot, feel free to tell me x