And afterwards I thought,'look what happened to me and how it hurt, yet here I am with another man's wife and children, even though he rejected them.' Am I any better than the man with my wife?
IMO yes you are. Your W rejected you. You made it perfectly clear that you still wanted her. She chose to ignore that. You deserve some happiness. Thoughts like this only continue to let her have a hold over you. I'm sure (like me) there is a side to you that wants you XW to have a hold over you but right now it's not healthy. If you'd gone out with this woman whilst still M then I would've agreed with your comments but you didn't so I don't.
Me 43 XH 45 M 2.7.88 Divorce 7.10.09 Kids D20,S17 & D15