*but he is the kindest gentlest man I have ever met.
He's not kind.
He's fucked someone else behind his wife's back after promising to be monogamous, building a life with her and becoming a fixture in her innocent child's life.
And I bet his AP didn't fuck him with him telling her he was happy, devoted, settled, committed in his relationship etc. That would be very unusual indeed. The fact that he's let slip he decided he loved you - after he started shagging her - suggests there was a question mark over who he loved. I'd say she was given the impression he had feelings for her and may well leave for her.
He took your agency away when he had an affair; you had your right to decide if you wanted to remain committed to and intimate with someone who was now intimate - emotionally and sexually- with someone else.
He lied to your face and by omission repeatedly.
He publicly betrayed/humiliated you too - other people knew about his affair and had to let you know.
He felt entitled to do all that.
None of that is kind.
Not remotely so.
You've had the rose tinted glasses on. You mention gentle - have you been in abusive relationships before? What happened with your child's father?
You don't want to not recognise/stay with a level 5 shit man, just because you had level 9 shit men before him.