Yeah, what sandrawg said... it's really hard to let go of the fantasy that things CAN be different. I know I used to beat myself up horribly for repeatedly going back to my abusive relationship ...and we didn't have kids!! I still have nightmares about going back to him and it's been over 10 years since I laid eyes on him.
I don't know if moving is the answer or not. Sounds like your kids might benefit from some stability in at least one area of their life right now. Perhaps if you focus on creating and maintaining strong boundaries that would be a very healthy model for them as well. Not to mention it would be best for you, too.
Just like an addict who relapses, we just have to get up, dust ourselves off and start again. No reason to beat yourself up. Just do what you have to do. After all, you're probably getting better and better at it so maybe this time it'll stick, eh?
It's okay. It's just a part of learning. ((((Hugs))))