Yet, in my cheating "fuck anything that walks" playthrough, I did feel kind of like the stereotypical asshole MC.
Yet the story (or at least the dialogues) didn't change.
The cheating was out of character (in my opinion) but then why give the option?
I think below is a great idea:
And it may not be that much work, just different dialogues and altering a few key scenes.
The last scene in the present version
doesn't make a lot of sense on the cheating path, because you were already fucking her, so it's not a reward.
If you do want to keep the scene the same, then the more-or-less-good-guy MC should at least feel bad about it through his internal dialogue.
Of course Jamie didn't know about the cheating, so her plan could still be the same, but the MC's response should be different, at least internally.