In my case, my H is good at compartmentalizing so I know that most of the time, he doesn't feel that shame and guilt from looking at me. We're able to have a good and fun relationship. But when I remember something and my demeanor changes and he realizes why, that is when he gets a wave of shame and guilt and wants to just shut down, rewind a few minutes to where we were.
May, I know some time has slipped by since you made this comment on Christmas Day. My two cents - your husband will never come to grips with his failings as long as he compartmentalizes it and goes into some sort of denial when he faces it. You mentioned that he is a faithful Catholic, if I recall? I'd recommend that he find a local Catholic men's support group (OK, it will have to be via Zoom) where he can talk about things, especially his A. It's my sense that he will not fully get past it if he is denial about it. Those men will hold him accountable, which hopefully will help him be accountable to you as well. Also, when his actions are placed in the perspective of the failings of all the other men, he should begin to feel less shame. He will find parallel stories and hear how the other men saved (or lost) their marriages or others in their lives.
If I learned anything over my years, it's that suffering alone is not a sign of strength -- look at what DB has meant to all of us. Also, that as we stagger through our lives and all the complications that go with it, we need the support of men and women who can hear about our failings and our fears, and support us through recovery. A men's group will provide some level of safety for him to begin those initial steps.
