We really are in such a similar sitch. I also kind of "left" my M when someone came along who I thought might be better. I certainly had left it in my head and it took me about a year to come back.
Ditto! I think that is where my W is right now, although one will never know! Maybe when things get tough, she really does reach out for someone to make her feel good & give her that happy euphoric feeling at the moment.