Screw the OM! He is screwing you through your wife. Some of these OM can be downright dangerous too, figuring out who and what you are and all and if they can have leverage on you.
Of course the wife opened the door.
Its a favorable cause to help "knock the OM off the wife/gf". You can't do this directly, and most of us aren't in the proper positions to do it with a direct confrontation as the wife will defend the OM and can draw closer to him. Also she handed him some of your power and over time maybe all of it, so it will be tough to face someone who has been so empowered at your expense.
Find out if the OM has a wife or long term girlfriend that does not know he's with your wife.
Collect enough conclusive information proving that he's sleeping around with your wife.
Find a way to communicate with the wife/gf, preferably in person. At a lunch a place they will deem safe. Tell them the story, to provide them the information so that there is not another fool out there.
The other way is if this person is part of your wifes workplace, is to find out if their ethics policies prevent such a relationship. If you have proof of stuff going on at work, thats even better. You provide your case to HR and to the Manager of your wifes affair partner. You do it in a calm and collected matter, just provide the information to show that he's breaking ethics.
If this person is part of law enforcement or any special agencies. Some departments don't tolerate this type of behavior as it does not fit their "image". It depends on the department and the location. If you can't do it from the department where he works, you can contact a neigboring department or internal affairs or another special agency.
Sometimes the FBI is friendly enough to help in affair cases where another agency is involved, because usually something else dirty is going on.
You can also provide the information to the guys parents or his church if he does this. Remember, you want to provide the information and not plead a case.
Stop being a victim, knock that OM off your wife.
Also if the guy comes into your house, in many states you are allowed to put a bullet in a trespasser if they come into your property.
The other thing you need to do anyway is to take care of yourself.
Mind, body and soul.
Study, get better at your job or prepare for other jobs Work out, take a martial art add some new hobbies Church, study, spiritialism, routines, self-love, sharing, etc.
