I would confront him about the A, but do it very matter-of-factly. Something like, "I know about your A with... I do not appreciate your lying and blaming me to cover your own insecurities, inadequacies, shame and guilt. For once act like a MAN and stop blaming women, especially me, for your problems."
Then end it. Don't call him, don't respond. Don't do anything that has to do with him.
When you mention something like I mentioned above, it shows him that you have confidence and will not be treated like a doormat any more.
He may end up leaving you, but do you really have such a low opinion of yourself that you would take him back while he's with OW? Show him strength and confidence.
M-43 W-40 2D - 9 and 5
Emotion, yet peace. Ignorance, yet knowledge. Passion, yet serenity. Chaos, yet harmony. Death, yet a new life.