Thank you so much for responding! I got the impression that there were not a lot of WAWs on this board. Hopefully, we can all help each other by seeing one another's perspective. While I certainly can't speak for every woman out there who leaves a marriage, I can tell you what I experienced, what drove me to that decision, etc. If that would be helpful for anyone, then ask away. I find that seeing things from the opposite perspective can prove invaluable.
I've done A LOT of reflecting since I left. (Like all night every night). I will say that I've come to the conclusion that it wasn't entirely me and it was entirely DH. It was both of us.
I do want to touch on a couple of points you made
1) The MIL. I absolutely agree MIL and DH are a package deal. In fact, when we first went to therapy, he said "I'll cut them out if you want." I told him that I did not want them cut out, I wanted limits and boundaries placed on them. That was the issue for me. For instance, for years when MIL would bad mouth me to DH and family he would just sit there . The correct response would have been, "Hey, that's my wife. Please knock it off." But he was very scared of her. I actually feel badly for DH in this regard. His mother is not a bad person, but she causes problems in his relationship. Both his high school and college girlfriends broke up with him over her antics. Other DIL(his brother's wife) didn't speak to her for the better part of a year. Poor DH is in a tough spot with her and, honestly, unless he learns to stand up for his SO I fear he will have the same problem if he remarries. THAT SAID, I absolutely have to own my part. When we got in marriage therapy, DH did start setting boundaries with her. Where I really messed up was not letting the resentment go at the point. He was handling it and I should have just let it go.
2) The 3rd child- Yes I was probably irrational on this. We'd been planning the child for years, DH had desperately wanted the third. And, to me, it was an abrupt about face right that was occurring right at the end of my child bearing years (38). I agree it wasn't logical, but I grieved that child. Really, truly grieved. It was beyond hurtful at the time. But it was probably the best decision.