They've told me that they're happy not to be hearing her name, the constant discussions, the gaslighting from him or me being so sad and angry - I'm doing so many things for myself that they love for me (more like forcing myself), and they seem to be thriving.
That and his whining to them about not being told who his friends are, he brought his obsession with her into your home to the point your kids were sick of hearing her damn name. Right there, your kids knew that was more than a friendship. She was a constant oppressive presence in your home through his actions.
And he's still not taking responsibility for your split caused by his EA.
They're happy for you to be out from under his EA partner and his hobby obsession. That's good. But it shows they have been affected in a negative way by their dad and his obsessions.
You have a good idea of what his behaviour needs to look like before you try to reconcile. But given his lack of taking responsibility and trying to make you the responsible party for your split, do you think those goals are realistic for him? He seems to have a view of himself as this poor, put upon victim who just wants to have an affair and go on trips with her while you sit home being patient. Even his kids know he's full of shit.
I think you need to put a time limit in place for genuine change. If he keeps up his victim stance, you could be sitting there till the cows come home because he sounds a bit narcissistic and he's not going to admit he's wrong.