To be clear, when I said "Nice Guy Syndrome" I mean the disorder described in the book "No More Mr. Nice Guy" and you're right - passive aggressive, manipulative, angry, doormat - all very accurate characteristics of who i've been the last 5 years.
I know it sounds like pride to set a boundary on the affair, but it's not. It's dignity and it's also severe concern for her health. What she's doing is killing her. She's down to 100 pounds, is sleeping 3 hours a night and is headed for Anorexia. If I don't do something now she is going to end up in the hospital.
I have her mom staying here now hoping she can help get her to eat (she says she doesn't have time to eat!).
BTW - how good a guy can the OM be? He dates this married mother of 2 and watches her go from 127 lbs to 100 lbs in 4 weeks and could give a fig? Any one with any compassion would end it before she has a heart attack.