You will continue to feel like you are responsible for the A. You will in time forgive yourself for the Marriage failings that you owned.
I still see you thinking about what he "might" feel or "pity" for him. You really need to understand that owning your part and forgiving yourself is the big step forward here. He is in "Love" land, understand that you are rational and he isn't. The goal is empathy and focusing on your self respect.
Nothing you continue to reflect on benefits you other than "fixing" the part of your responsibility. When the time comes you will realize you don't owe him S***. He stepped out and you didn't, that's the difference.
Keep focusing on you and "Let go" of how he views you and the way you feel.
Trust me, when you actually "Let Go" he will notice you.
