I understand your comments about being a perfectionist. I'm far from what anyone would consider perfect, yet I'm still considered very capable, moreso than H in many areas. H would tell you I'm a perfectionist, but I believe that's simply because he has such low standards. He'll argue and defend doing a sloppy job on something, then belittle himself later because he doesn't like how it looks when he's done. I think perhaps he has a very low self-esteem, though you'd never know it talking to him. He'll even interpret my different opinion as criticism. "I like red." "Really? I like blue." And with that I've just criticized him.
You really sound stuck. Not in your situation, but just in your head. A lot of analysis-paralysis going on. You obviously don't like any of your options, not that you should because they don't sound fun. But in spite of being painful, they are doable.
I'm curious that you're cutting off the people that care for you that are encouraging you to get out. If it was just one BFF that you felt didn't have a good handle on the sitch, I could completely understand that. But family too? Your therapist?
Can you envision your future at all? Not 6 months from now, but 5 years from now? If you consider your M, do you see your H being any better 5 years from now? Is he at least on that road? His issues aren't minor, and they're not something YOU can fix.
Alternatively, if you consider leaving, what can YOU do in 5 years? At least in that scenario, you would have control of the situation, which I think is something sorely lacking in your M, and a big part of what has you in your massive funk. You feel stuck from all angles. And your H isn't helping, as he sounds like he knows he has you where he wants you.
The thing is, like when you were separated before, it isn't a guarantee that you'll be done forever if you step away from your M. I know it's not what your H wants, because he's obviously benefiting greatly by your presence. But that is not him caring for YOU. It's also possible that the most caring thing you can do for your H is to walk away and stop enabling him. Again, it's not my area of experience to say, but something for you to consider anyway.
You said you came here hoping that someone would tell you that you should stay. It almost sounds like someone who is debating whether to leave their M for their lover. But your sitch is much more complicated than that. There is not another person. Your question is more about do you save your M or save yourself. What relief would it give you if someone were to tell you to stay?