But he's not really a great guy is he? It wasn't just one mistake, it was a very conscious and deliberate number of acts which - to me, and his ex-wife obviously - would be unforgivable. He didn't choose to discuss his sex addiction with his wife so that they could tackle it together. He chose to sneak away and visit prostitutes regularly behind his wife's back - and then presumably only admitted to everything after he was caught?
May I ask what your response was when he told you? My feeling is that if your initial response wasn't 'fuck off forever, you utter scumbag' then you have almost already accepted it. You've accepted him and his... affliction?...already. Which is convenient for him, because when you catch him at it again, he can say 'but I can't help myself, you knew what I was like blah blah blah'.
On the other hand, maybe he genuinely is a changed man. But I would be very, very cautious. And I would find it extremely difficult to ever relax, trust him completely and just enjoy the relationship.
If I'm honest, I thinj you had already decided to accept him before you even posted on here because your original post portrays him almost as a victim that is going over and above the call of duty. He pays more than he should? So fuck. He bends over backwards for his ex-wife? Damn right he should! A bloody good ex-husband? It's an utter shame that he wasn't a bloody good husband instead.
I'm sure you'll give him a second chance, but just know that he doesn't deserve it.
All the best.