Is he worth it and what to do?

Right there is this guy i know and he is okay when he is on his own, i walk to school with him, go to cinema with him like every weekend and i know his family. But when he gets around people he starts showing off and becomes a ******* ********. I was going to go meet a load of my friends today, until I found out he was there because I know he would turn into a ****. I saw my brother in town when i was with him and my brother hit me in the arm as a friendly joke, my 'friend' just carried on as normal until i get on facebook and then he starts taking the mick out of me on my wall so everyone could see? So i want to knock the hell out of him but is he worth it, i know if i do this i will be excluded from school and my friends that are also his friends may take sides with him leaving me as a loner. Also his family wont like me. If i don't do anything he will carry on being a idiot, ruining my plans and annoying me. So what should I do?