OP,
I am going to be completely frank with you. You seem like a guy with a good head on your shoulders. But you aren't happy with your wife at all. She likely feels the same way. Just get it over with and divorce her. You, and your kids if you have them (can't remember), will all be better off if you cut your losses and get out. The only thing you are risking at this point is making yourself look like a POS to members of your family, her family, your profession, and community. Relationship fall out is a real thing. It can impact other parts of your life. Trust me on that.
Just file divorce and cut your losses. You will be a much happier guy with your freedom back even if your wallet will be a bit lighter for a time. This kind of 3 some thing is just the latest evidence you need to end things now and not later. Sure, you can try the cheating avenue. But again, this can impact other parts of your life if the wrong people find out. So tread carefully.