@Iamtrash,
If this is a critical point for both of you, perhaps offering to take a poly might be helpful? While you can't undo the proof that it happened, you might be able to prove that you weren't lying about not remembering it? (There are lots of reasons a person legitimately might not remember such details. "Trauma brain" is an expert at blocking out that which hurts too much to remember)
The other thing I want to offer is this - you noted that "There’s no coming back from this.". And it sounds like it probably is. I don't want to offer false hope. But "over" can be a point in time. Several couples on SI have gotten divorced only to remarry again later. People have been asked to leave, and then offered to come back again later when things have cooled down a bit. How you respond to this event, and more importantly, what effort you put into moving forward, is critical right now.
"You don't believe me when I'm telling you the truth" is not much of a motivating factor for a betrayed spouse to reconsider staying.
"I know you don't believe me, but I'll do everything I can to help rebuild that trust, including a poly if it will help" might be a better response.
"I'm sure it was horrific for you to see that tape. I'm not proud of what I did, and you don't deserve the constant pain and loss I've caused you. If I were you, I wouldn't believe me either. While I can't go back and undo what I did, I can promise you that, no matter what happens between us, I will never stop working to be a safer, more authentic and more honest person, and I will do absolutely anything I can to help you heal, and to stop hurting you more in the future. If you need me to go, I will, you deserve to be happy. My plan is to keep working on being a better person, no matter what. I hope one day, that might be enough to consider a second chance" for us. Because you deserve better, and because I am not capable of respecting myself if I keep being this same, broken person." is the message that needs to be delivered, by both word and deed.
Rebuilding trust takes sacrifice. It takes humility, and courage, authenticity and vulnerability, and a willingness to go to painful places and to throw yourself under the bus when that's where the truth takes you.
One last thing, and this is the part you may not like, but maybe need to hear.
Re-read what you wrote. I get that this is the WS forum and that you are venting, and that's all good. But this post was 100% about you, and your pain. Nowhere did you empathize with your spouse. Nowhere did you "own this" and say, "My God, I can't believe how much I destroyed this man's life" or even "I hate myself for causing all this". You are pissed at the AP. You are upset with your spouse's response. You seem to feel that you are being unfairly labeled as a liar. But I don't see ownership. I don't see remorse. I don't see contrition. I don't see empathy. And while I cannot promise you that having those things would save the relationship, I can almost promise you that not having them WILL end it. Because who wants to forgive someone who hurt them and yet feels owed the respect they themselves can't/didn't give in return?
I wish you the best Iamtrash. Please try to take this as a moment of decision and of growth. Because that will bring meaning, purpose and resolve to the situation. It will bring hope. It will allow you to rebuild the respect and trust you lost. But only if you can allow yourself to hurt like you need to.
[This message edited by DaddyDom at 7:54 PM, March 18th (Thursday)]