"no longer carrying the guilt which turned him into a horrible person"
"Guilt" didn't turn him into a horrible person.
He was horrible to you because he wanted to be. Because shagging another woman behind your back made him despise you.
It was not guilt.
If he felt so guilty, why didn't he end it
Why wasn't he nicer to you?
That he is making such self-serving, self-aggrandising excuses for his deliberate, continual choices to treat you like shit, and you are accepting them shows that his remorse is false and you are still too shocked to deal with the reality of what has happened.
He had a relationship with another women behind your back.
He lied to you and treated you like a fool.
He treated you badly while he had another love interest he preferred.
He got dumped and so he is still with you.
He never planned to tell you that your marriage was a sham.
This is not just about a good man making a tiny little mistake and then being a little bit mean because, being such a wonderful guy, the guilt was too much.
This is about a selfish, dishonest liar who has ripped your family apart because he fancied a shag.
Maybe you can forgive him. But not until you both face the reality of what he has done. And not until he is truly sorry.