John....

You are doing the right thing. ending a marraige in the midst of an affair will in most cases lead to a disaster. I would suggest that you really give your marriage 100%. Talk over with your wife how you feel, be honest. You have nothing to risk at this point. Salvaging a marraige is better than jumping into a relationship with a misstress and then having that relationship end as well. It just isn't worth it. Takes guts to follow through with your plan.

Good luck.