there must have been something I was doing or not doing wrong.
Why do you say this? Was this the case when you had you affair?
It's not about you not doing something, it could simply be he enjoyed the attention and getting his ego boosted.
What ppl need to remember here, is you are the same 2 ppl even though you divorced and remarried.
Yes he forgave you, but he hasn't forgotten and it's not like he has used your affair over your head for the last 25 years is it?
I don't think it was revenge on his part, he's simply trying to find an excuse to justify his behaviour like most ppl in affairs do. It's a natural defence mechanism of human beings.
He seems sad now, but he's feeling sorry for himself, not for what he did to you. It seems he misses her and that's causing his sadness. He's still saying what a good person she is and that would piss me off, but if he says she's bad, then that makes him worse.
I'd just find an affair while I was so ill unforgivable tbh.
That sex with an OW was more important than me, would be a point of no return.
Normally, my opinion is if one person cheated first, they should be equally forgiving, but the cancer changes everything for me.
Perhaps time and space apart will help you gain more clarity on this, but it's a tought situation.