Wow, I never come in here anymore and wander in to find this.
I think you have made a brave decision and you are handling it with great courage. Yes, the kid part of this whole thing is very heart-breaking, but I know that you and W will do right by them, whatever it is that they may need.
When I finally closed the door on my marriage is when I finally felt so much better. I know that is dangerous to say here at DB newcomers (which is why I don't really post here anymore), but it is true for me. You have put an amazing effort into saving your M and you are right to feel justified that you have done everything you could have done.
Sounds like you have a good plan for moving on with life, not that I am surprised by that!