Maybe hers isn't far underway. Many of ours do not care what we think and would play us like we are imagining things with respect to their affair.
I am not sure if I would have confronted with the evidence you have, I'd like more damning evidence.
If you think you can scare OM by yourself... Usually it does not work, its why the people here find a wife or girlfriend and show the evidence to her. She will usually spend alot of time on her side putting the OM through hell. Those OM's usually drop off then.
You can't worry about OM's feelings or whathe would do if he was in your shoes.