I guess my "detaching" reply didn't answer your deepest question - on how to "break the cycle". All you can do is work on you, control you and make you a better (the best) person.
There are no sure ways to fix your M or fix your W. The only hope you have is to make you this incredible person, one that she was attracted to before, or make yourself even better. If she snaps out of it for you or for the kids, she will do it on her own - not by you reasoning with her or pressuring her.
I know this isn't easy for you in this stage. I'm past this stage knowing, with more certainty my future. You need to balance yourself, knowing that your life will be great with her or without her. Not easy to hear, but something you need to accept so her inaction doesn't continue to pull you under.
