Hi Lea, I truly do want nothing but the best for you and your family. Stop beating yourself up. Your H's decision to have an A has nothing to do with you. This is all about his weaknesses, his insecurities, his lack of maturity, and his unwilligness to honor his vows. All of us spouses can make the justification to have an A if we want to. Some of us are simply stronger and more honorable than others. He chose this, let him sit in it. Thats why I keep suggesting going dark, he has been able to push your buttons whenever he has wanted to, it helps relieve the guilt he feels, and he does feel guilt, how could he not.
I would suggest to not respond to any dig he takes at you. Don't give him the satisfaction. Don't lower yourself to his level. Let him be a fool by himself.
Until you can detach, he will have control of your emotions. He has had control long enough.