If you have a talk, I do not recommend revealing your knowledge. You can say you don't know what her relationship with OM was, but you think she was looking for a new husband, and the thought of that upsets you. You think it is wrong to stay married to one person while looking for another husband. You don't know if she is still planning to move out, or if what happened at work changes that. But you are not willing to support her while she looks for another husband. So if that's what's going on, then you do think it's best that she move out. You married her for better or worse, not til something better comes along.
And then just see what she says. You haven't made any ultimatums there. You are just saying "If that's the case, then the marriage is not going in a direction I want to go in." And you don't claim to know anything, you only know what she has told you, or what what was said on the phone calls with OM and OMW. It lets her know that you do have decisions to make in all of this too. It is not all up to her.
