If you haven't already read Codependent no more, by Melody Beattie, you might find it really helpful, just in terms of changing your thinking about your role in his life.
I have a suggestion. At some point during the day, go to your front door. Open it and just stand at the door way. Now just let your mind wander. That door is open, the only thing holding you back is your own prison. I don't mean to sound all "airy fairy" but honestly, it is that simple. You are a free person, you are not your Husband's keeper. Sure, he has lots of issues, which he won't get help for, but those are not your issues, he is a grown man, a separate person.
If you could fix what ails him, he would be a fine, upstanding (working) citizen. You can't, you never could. Staying or leaving, it really is just your choice.
Until you leave there will be no way for the FOG to clear, (fear, obligation, guilt). If you are still stuck, trying taking a week or two away, give yourself time to see things really clearly.
You didn't Cause it, can't Control it and can't Cure it (the 3 c's).