I guess my boundaries are a little different than what yours were though and it may be ego-driven (but really just my values). I will not stay in an open marriage. (and I know that "stay" is an arbitrary word that has no timeline)(the word stay to me is my weakness and I think she knows it - so I am now thinking "Be" instead of "stay").
She does not mention or flaunt OM in any way. But she knows that I know. She avoids and lies about it all together. It is "completely" underground. Only by my observations and her flawed stories do I know what's going on any more. She has hidden it from everyone - except one of her friends. If I shut my eyes real hard and didn't care where she was, I would not know it was happening. I just do not think I can continue this way.
If I do not enforce my boundary, I believe the A will continue for who knows how long and I will feel weaker.
I do not think that by stating this boundary it will change her (and I do not understand why as I say that I would change for her). So the action will have to be S&D.
She hasn't really been my wife in a long time anyway.
Me-45 W-44 S21, S18, D15 T-27, M-21 BD Jan 2014 PA revealed March 2014 In-house separation - April 2015 I filed - Aug 2015 She moved out Oct 2015