There's a bigger problem at hand as well: Your wife's friends.
They seem OK with her flirting and/or sleeping with the OM. And you seem to be the "problem". If her friends were real friends they would say, "Bring your husband, the OM isn't welcome." But apparently they are loyal to a man who wants to steal another man's wife.
This is her social circle. People tend not to rise above the moral base-line of their community. It seems you wife's new social circle is A-OK with adultery.
Take Starsky's advice.
Also the first half of the DR is about solving relatively benign marital problems. It does, alter in the book, talk about a Last Resort Technique, After the Last Resort Technique (going dark) and ultimatums. Those are all part of the arsenal.
