I definitely will have to let W know that what she is doing is unacceptable and I won't participate in an open marriage. Then what?
If I'm not moving out, I'll still be allowing her R with OM to continue in my presence. Right?
"Love Must Be Tough" has advice about this, but it is a dilemma. Here are your options as I see them:
1) Ask her to either stop seeing OM or move out. She can decline to do either, then you can decide what you're going to do
2) Ask her to leave the bedroom and sleep somewhere else. If she declines, you leave the bedroom and sleep somewhere else in the house
3) Pursue a "controlled separation" -- consult with your lawyer about your options. In this scenario, you would legally separate, but do it with an eye to reconciling down the line. There's a book that will guide you through how to do this. In this scenario, you move out or she moves out for a predetermined period of time.
4) Pursue an "in house separation" -- parallel lives, same house, not acting as spouses but still co-parents.
In any of these scenarios, you change how you treat her. You do not offer intimacy, you do not tell her how you're feeling or what you're thinking. The less she knows about your mental state the better, make her wonder. You don't make dates with her, you don't do acts of service, you go out and GAL your ass off. You treat her as a friendly co-worker. If she asks you to do her a favor and it's not a major inconvenience, you do it. If it's a major imposition, you don't.
You lovingly detach. i.e. if you are not committed to me as my wife, then you do not get any of the benefits that come along with that. Then, you make those benefits that she is missing compelling through your actions -- you become the man that only a fool would leave, but she is not allowed to have.
The situation [censored] from all perspectives. However, you can get into the driver's seat with regard to your own side of this. You dictate the landscape for yourself.
--Accuray
Married 18, Together 20, Now Divorced M: 48, W: 50, D: 18, S: 16, D: 12 Bomb Dropped (EA, D): 7/13/11 Start Reconcile: 8/15/11 Bomb Dropped (EA, D): 5/1/2014 (Divorced) In a New Relationship: 3/2015