I'm guessing you're in a relatively young age group (guessing grade 7,8 or 9 in school) Because you don't get thiose kind of jerks past that age, well mostly.
What's my opinion, as a friend I'd say to that guy the next time he tries something 'look I've had enough, either put up or shut up.' Thuis is your warning. If he doesn't listen and gets too close (like reaching or pointing or anythign with contact) Then smack him in the nose with your fist (only if he's in a close reange).
As a magician I'd recommend you just stop performing for now. Sit down and practise your heart out, get good with coin or card handling, very very good. If he knows all your stuff then you better practise it much more to hide it better and learn loads more stuf and WELL (so he can't figure them out aswell) When you're ready (give it months) start performing again but don't go over to him and try to show off, still avoid him. But if he does show up again then at least you know your stuff better.
As a man of vendetta I'd start screwing up his magic whenever he performs. And if he doesn't then there you go, next time he jumps in just say 'Why don't you bring your toys in tomorrow and show us all then!'
That'll shut him up. If he does follow these instructions then get ready to switch places and become the jerk yourself