Starshyne, It's good that he is trying to end it. If the OW knows he wants to end it, chances are she'll react by pursuing and begging. That's exactly what you need to NOT do. Be the person he wants to be with. Give him space. I gave my H lots of space, but not so much that I was a complete doormat.
OW in my sitch was also a "mad" woman (still is). Former coke addict; bad mother; horrible marriage. I think some men are attracted to that sort so they can feel like knights in shining armor and thus, feel better about themselves.