10 POINTS if you help me help him?

last year I liked this really sweet, shy guy Lukas. He's really smart but a jock too. He was always into soccer and over the summer he got really muscular & hot from it. So now he ACTS really vain, pervy, and otherwise a jerk. I go to a different school now but i saw him last month and was sooo disgusted! He's totally different! I really want to help him, but idk what's best for him and I don't know how to help him even if it is best for me to try to change him back to how he was. I might only see him 6-7 more times in my LIFE so I don't even have much time!!! I REALLY owe him because of a long story where he basically made me realize what an a$$ i was, so now it's my turn and I can't just let this go. He sort of isn't a complete idiot YET. See, some of my friends who still go to school with him don't put up with him so when they yell at him for being pervy he gets upset because he has a crush on one of them and she USED to like him back, but now she hates him because of the above said. He's still really sensitive inside and I think he's just acting like this to get popular, so I think there could still be hope:) but idk. I don't want to make things worse! What should I do?!? Please don't tell me that i can't change anything. I REALLY want to help him out. 10 points if helpful/specific