Over, I can see you're doing what you can and need to, to survive. I think you're a brave, resourceful and resilient woman. You wouldn't have got this far otherwise and I hope you begin to trust yourself and your own intuition about what's best for you in this situation. Nobody here knows what that really is as we're not you.
I absolutely respect your need to do this in your way. It's really important that you have control over your life and what you choose to do with it. (I know I'm repeating what a lot of others have said but I suppose I want to reinforce it.)
Over, I've no doubt at all that you love your children. I imagine you love them fiercely and are wound up in knots worrying about them and how to protect them a lot of the time. I can really hear you're doing the best you can and that for a lot of the time, staying put has and sometimes, continues to feel the least worst option.
I also know that once you've had children with someone it changes any relationship. We become threaded together in a way that means it's difficult to untangle isn't it.
I want to add, I don't think you're a failure and there IS hope. There is nothing stupid, pathetic or wrong about you or whatever other judgements you may have about yourself. (I don't expect you to believe what I say but I want to say it anyway, just so you get to hear some other people's perceptions of you). However ashamed, angry or humiliated you may feel, you haven't brought this upon yourself.
I'm really sorry that you felt bouyed up with a 'false confidence' that then led to it all crashing down again. It must be like trying to scramble up an unclimbable mountain right now and then I was thinking, another way of looking at it - is you tried. Which is what you'd said you wanted to do. You wanted to give him a chance.
See, I think that's another example of your compassion and sensitivity toward him, your loyalty, committment and tenacity to the relationship. There's nothing wrong with any thing that you're offering, what's wrong is how he responds to it. You don't deserve to be anyone's emotional punchbag.
I'll say it again- One day, maybe you'll be able to offer those qualities to yourself. To be compassionate and sensitive to what you need, to be committed, loyal and tenacious in loving and knowing yourself and doing what's best for you.