"More marriages might survive if the partners realized that sometimes the better comes after the worse."
I know it is hard to forgive and move on but it is probably far better to just accept what happenned and see what you can do about making your marriage happy...make him wonder why the hell he even had the A in the first place when he has a wonderful W and family at home. Do not focus on the actual A as the problem but the true problems in your relationship as the issue...fix the relationship issues and hopefully all will be solved. (I know easier said than done...and your relationship IS forever changed...but make those changes for the better!)
"Friendship is like peeing your pants: everyone can see it, but only you can feel the true warmth."