Keep being the good Mom that you are. It is so tough with the kids, because they do sense what is happening and unfortunately, will work it to their advantage. Even if they are young and not really sure of what is going on. Dad isn't going to help, because he doesn't know how. He probably just wants to be the good guy and if he is anything like my soon to be ex... he will take the easy route. Kids need structure and need to know they are loved... IMO, discipline is part of that love.
Do for you, do for the kids. Get away from the chaos as often as you can. Give yourself room to think and plan and then do what is best for you.