Stars, I've been following your threads and didn't feel I could add anything of value, as all the other posters have added far more eloquently the points I would have made.
However, this self doubt you have, I have to say I went through this whole thing myself.
I didn't leave, as just as I had had enough he'd be lovely. And then slowly we'd slide back to the awful scenario.
Personally I felt I was fighting to save my marriage and my children's home. Everytime ex was nice I was clutching at the crumbs hoping we'd turned a corner and that maybe he would now be a decent person to my children and I, and just as I let my guard down, or started relaxing he'd be a million times worse.
But those quiet times, those times when he was behaving as a decent normal human being, kept me hanging on for far too much longer than I really truly should have.
I'm not saying leave him. That is completely and utterly your decision to make when the time is right for you.
To be perfectly honest, if it hadn't been for a much wiser police officer, who had seen it all and could see right through ex's act. I would probably right now be in a very bad way.
good luck with everything, I hope you find a clear way through this, you are a lovely brave person, who deserves a happy tranquil love filled life. Not just the quiet before the inevitable storm.
Trust me, I surprise myself at the sheer joy I get from completely mundane things, like ordering take out because I cannot be arsed to cook, something I was never allowed to do whilst with ex!
Take care.