It's written somewhere in the book...and I'm paraphrasing: become the person, that only an idiot wouldn't want to be with.
OK, I'll bite, and I'll get straight to the point:
Why would your husband want to be with a wife that would allow him to say "I love you" to the woman with whom he is having an affair, in that wife's presence?
If you two were single, and just met, would this behavior be attractive to him, or repulsive?
I'm not trying to be mean, Abbey -- just challenging your assumptions and trying to make you think. There is a cavalierness and a flippancy to your attitude toward your marriage and how precarious it is right now, and to your husband's infidelity, that I find disturbing and a bit odd. A defense mechanism of yours, perhaps? (which is UNDERSTANDABLE).