I wonder if his anger is because his AP is now pressuring him a lot to leave you, and he’s still in the home with you?
He hasn’t "decided", but the fact that he hasn’t left IS a decision, and she knows it.
I think she exposed the affair because she got tired of him promising to leave you for her, and he never did. Three years down the line, she’s deep into the affair, he hasn’t done anything to change the dynamic for her, still sneaking around….which means he didn’t want to change a damn thing. He was happy to keep her as a side piece, and wanted his home life just as it was.
He didn’t want her, and didn’t want the mess he’s in.
He may very well have felt like he trapped himself in a completely screwed up thing, and now it’s a hornet’s nest, and he’s saying he isn’t happy? Of course he’s not happy. He has ripped his life apart, by his own doing, and he has no way to make anything right.
He probably thinks there’s no way to repair the damage to the marriage. If you truly want to reconcile, you have to make it clear to him that you want to repair the marriage - but also make it clear that the path to that is completely cutting off the AP forever, no options on that. And that as long as he is in cont with her, you are not willing to be his wife or friend. That this isn’t HIS choice at all - it’s actually YOUR CHOICE, because there are two of you in the marriage, and you both get a vote.
I told my WH that he was free to go to his AP, but once he did that, I was no longer his friend, wife, or anything else. We would be no contact, except for a parenting app that would be anything daughter-related. Any other information would be relayed via attorneys. I would not see him, speak with him, or contact him ever again, because he would have chosen another person to share his life with, and that eliminates me from any further role in his life at all.
He was in shock, because his fantasy didn’t really account for the fact that I would be gone.
This reality resulted in his immediate phone call to AP and telling her that they were done, it was over, and they would never be in contact again.
That "love" they had went "poof" in that moment, according to him. He said it woke like a bomb went off in his brain.
You have the choice in this. You can tell him that YOUR CHOICE would be to recover the marriage, but as long as HIS CHOICE is to hold onto her, your only choice has to be to keep your soul alive by going no contact with him. And that there is a window of opportunity for him to come home, but the window is closing more and more every day.