This is the most painful part of the affair... when you find out not only your wife has betrayed you, but people whom you thought to be friends of the marriage turn on you AND the marriage as well... It really is a testament to how uneducated and how immature adults can be.
Your wife is a talented politician that is clear. And the classic "I just want to be happy" is a classic excuse for an affair.
I would inform whomever you can that you want both of you to be happy, but you aren't goign to CHEAT on her to find that... And again ask them to at LEAST supoprt your marriage as far as NOT accepting the OM into their lives. Many are willing to do this I find... they won't speak UP on your behalf, but if you ask them to OPT OUT of the drama, many are willing to do this, but you have to ASK them... otherwise they will just do what your wife wants...
If you feel it may have impact you can approach the OM, its not a tactic I often reccomend, but if everything else fails, this won't hurt.... you simply ask him to STEP ASIDE and respect your marriage... tell him if HE was married you certailny woudl'nt be attacking HIS marriage... most often this results in laughter, but if you have nothing left, this has a small chance of impact...
I would save that as a last effort though... unless you can do it in public.. THAT can have an effect... show up at a party you wife brings him to and ask him in PUBLIC to stay away from your wife "please".. respect my marriage and respect my wife and I and our marriage by STAYING AWAY from her...
If you do this in public, it humiliates him... THIS can have impact...
SHAME can resonate even in the most callous of people...
