I don't have much advice to give right now, as I believe you have it figured out. You know what is best for you, you just have to figure out the best way to do it, which I'm not sure any of us can really help with since you know him best.

I do want you to know that you are being extremely rational about everything and I find it really inspiring that you can sit down and work your way through your feelings and his feelings in such a calm, balanced manner. I think you're doing a great job. Just remember not to be too hard on yourself. You said it yourself, he's responsible for himself, just as you are responsible for you. Do not punish yourself for things you know are impossible to do, for things he must do for himself. I think you should be proud of yourself for really working on this relationship, and then knowing when to leave for your own health, safety, and happiness -- most people don't do or know either of those things.

Really, I'm just so... in awe over how well you are handling this. Please be sure you give yourself plenty of time to grieve and heal. You are an amazing, wonderful human being worthy of love and happiness.