It's very hard, Healthy. I struggled a lot with that when I first came to SR on another board. People told me one thing, my heart and gut told me another. Right now, my heart and what I call my HP is telling me to stay, work on it, don't give up yet. Totally contrary to what people tell me. Especially the couple of friends I have confided in. But ... it's very easy for them to say. I have to life this life, not them. And so I get to make the ultimate and final decision.
That said, you need to do what I right for you. Have you tried talking this out with him? Or with a therapist who is neutral? I think we always know the right answer, deep down inside, just sometimes we have problems finding it or admitting it.
I'm not sure where the dividing line is. I went through a horrible patch when I had DD, I had post partum depression that turned into long-term depression. AH finally made a dr's appt, and literally put me in the car and drove me to the dr to be put on meds. Was that rescuing? Or was it love and caring? I didn't find a bottom to my depression, but his actions made me realize how much I was hurting them. Now, I no longer need meds and manage quite well. Did he overstep or would I have done something serious had he not? And what makes that different from me stepping in and telling him he needs to look at his life and what he is doing to us? I don't know. How can I give up on someone I love? Maybe when he has given up on himself?
I don't know any of the answers. Just trying to follow my own heart and Higher Power.