Most Helpful Girl
Not good. He seems like a decent guy because he wants to back off. However your girlfriend here seems like she could have kept doing whatever they've been doing. She said that she appreciates him wanting to back off but at the same time is "trying to be cool with that" which isn't that great. And he said that he doesn't want to keep her from being "100%" with you so clearly they've been doing stuff behind your back. This girl is not worth trusting or being with, she obviously has a thing for this guy and there's no point in being together with her anymore.
Most Helpful Guy
It seems like they have a thing to me but from what they're saying the guy probably wants to back off so she can give 100% to you
I wouldn't stay bro