I think you've had some really great suggestions here, May.

I am not sure if you want to talk about the A because you are fearful there are more details you don't yet know about, and knowing those details, while painful, might take away that fear.

Or if it is because the details of the affair are less important than hearing your H tell you that he takes responsibility, that it was wrong, that he regrets it, feels remorse, and that your actions around the SSM are not an adequate excuse for it in his mind.

Is it both?

My H and I do not talk about his EA any more. It was a more minor matter than the behaviour of your H, so perhaps not directly comparable, but I did want all the details in one go, and he did answer my questions at the time. When more came out in the months afterwards, I felt very betrayed and it look me a long time to understand that actually, he hadn't told me this one or two particular details not to hide things from me, but because it was genuinely irrelevant to him. It wasn't irrelevant to me and he was able to validate that feeling. I have been able to accept that I will never KNOW every single little thing, and that the important thing is that it is not happening now, and he had been faithful to me since it ended. He is very transparent now.

I wish he could say 'that was totally wrong and I regret it, and you didn't deserve it no matter how our marriage was at the time.' He has said some version of that, but he will also talk about his own position - that he felt burdened and lonely and unappreciated and controlled. I have chosen to hear this as him wanting me to know where he was at the time - wanting me to understand his heart - rather than him wanting to make excuses or put some of the blame for his actions on me and my part in our struggling marriage. I have also told him I take full responsibility for my part in the marriage and for how awful it was for both of us, but I don't take any responsibility at all for his behaviour, his infidelity and verbal abuse, and that he is always responsible for his own actions. He still struggles with this and is apt, if he gets grumpy and rude, to say that he'd have been gentler or kinder if only x hadn't done y. I've told him I find that kind of talk immature and unattractive and whether he believes or accepts it or not, he is still responsible for himself. It's an aspect of his character I find difficult. But I leave it with him. I don't poke at it. I just put responsibility back on him when he tries to hand it to me.

It is not perfect and I suspect my H has been willing to be more transparent verbally and give a clearer account of himself verbally than yours has. I also think H's in this position will have to - over a number of very many years - take gradual responsibility for who they are. All you need to do is keep to your boundaries. They may not want to pick up their own mess, but it doesn't mean it falls on you.