You cant help how you feel, but adults can control how they act.
Action's have consequences. The likely hood of his ds having nothing to do with you lasting is low.
Eventually that will probably change.
My dd has a relationship with her dad & SM who started as an affair. She's an adult now. She loves him, but doesn't particularly respect him. His affair was just one of selfish decisions that he made through her childhood and around his relationship.
She has a very different relationship with me and her step dad my dh and always will. She also is in therapy for all the abandonment issues he caused as a result of his behaviour as an adult.
His family accept them, but it's a much cooler relationship.
As far as the happy and examples of successful post affair relationships.
Actually they have no idea if they have been cheated on. Once in life you cross a boundary it's easier and easier to do it. Pissed off, bored not feeling the centre of attention. Sex dropped off, kids driving you mad. Well if any one knows the kick of dopamine hit and affair brings. It's people who have had them.
I certainly wouldnt be saying my husband has never cheated on me, or was capable of doing it. And he hasnt ever had an affair as far as I am aware.
As for the way MM treats people who have affair. I think of them the same as domestic abusers. I havent ever in my life seen one that doesn't come with manipulation/gaslighting/financial infidelity and the removal of informed sexual consent.
What done is done. You both made your decisions part of that is accepting for some people their view of you and your relationship will always be coloured by your behaviour and choices.
But if that really mattered to you, you wouldn't still be in a relationship with him.
So if you want to stay, shore up your own self esteem, make sure you always keep your own income and worry less about what people think of either of you.