Thanks for posting on my situation. It's kind of you.
I read your whole thread.
It seems like all you have to do is let the OW dig her own grave.
State your boundaries to your husband, but don't punish him, keep the road home smooth.
Now...what attracts him to her? ROOT and Sara pointed it out well. She brings out his "bad-boy" side. She's wild, unpredictable, trashy, dangerous, but certainly passionate. I think, as you pointed out, you represent all that's good, true, stable, responsible, caring and respectable in in a woman. But, as you noted, you weren't interested in sex. It seems like the good old madonna/whore psychological complex.
For quite some time, he respected you, but felt more "alive" with her. She's desperate and pathetic. But people like that, who have nothing to lose, can be quite interesting at times.
On a personal level, I seceretly admire the recklessness and passion of people who feel they can take what they want and not care who they hurt.
I, too, am the nice, stable, caring, sweet, boring guy. My wife went aftera man who was very sensuous, charismatic, warm, passionate, a rule-breaker and as you guessed very un-employed. She went for the bad-boy.
Maybe, Joie, you are not soo sweet and nice. The paradigm I'm thinking of is strength and power without malice. In the Chronicles of Narnia, when Lucy heard about Aslan, the lion. She asked if he was safe. The beaver responded, "Heavens, no!" He's a lion, of course he's not safe. But he's good."