Why don't I just leave my screwed up W and M behind and find something new?
Because you still care about your "screwed up W and M" ! And you still care about your family. You are doing good man! Keep it up...if you can. Only you know for sure how long you can keep doing it. If you give it all you've got, for as long as you possibly can...then you will know for certain that you did everything in your power to keep your marriage and your family intact. If it winds up that you are reconciled...then great. If it winds up otherwise...you will know that you fought for something that you believed in...and somebody else ended it.
"Always go straight forward, and if you meet the devil, cut him in two and go between the pieces." - William Sturgis, clipper ship captain, 1830's.