How do I discretely let him know to piss off and stop ruining my social life?

There's this boy named Anthony, we've known each-other all throughout high school. He's one of those mentally-disabled boys that are semi-disabled, that are socially akward and different. His teeth and gross hygiene also annoy the heck out of me. He also is known to lie and make-up his life such as he says that he has this crazy friend named Monhour that would kill me by setting me alight whilst in his flame costume, also that he owns an axe collection, he's extremely rich owning at least three properties in America, he made up his own religion called 'moronosy', and the more controversial Monhour wears a Fursuit (Apparently Anthony has one too and the two go by the codenames of Duke and Ford) now your excuses are is that he's mentally retarded he doesn't know what he's doing, that's not the case he just has ADHD and he has full control over his doings I can tell. In class he sucks up to teachers and talks to them more then his colleagues. Referring to his fursuit 'Ford' he says that he goes out to fur conventions with his friends and picks up all the hot furry girls (has been doing so for 8 or so years without his parents ever caring or finding out) I asked a student counselor that accesses him and she says his mother keeps close watch of him indeed. Now that his only friend and companion Andrew ( whom he treated terrible like a doormat) including his girlfriend Daisy who dumped him flat on his ***, he comes out of no where while I'm talking to my friends (Friends that I have friendships with and I have spent months and months cultivating, I'm not really good with friendships) I can see him in my peripherals walking in the corner of my eye, he circles the tables for five minutes or more and expects me to welcome him and greet him, I try not to give him eye contact I want to let him know I don't want to be his friend after what he's done to me. Hasn't paid for the commission I've done (his excuse was that it wasn't good enough, It was I'm an amazing artist. He promised me money when he first saw it), won't show me in his fur suit as it apparently ruins the illusion after knowing him for 3 years and apparently trusting me, nearly attacked me and bit me, sent me death threats that his friend Monhour was going to kill me, sent me cut-throat signs and death threats, also on MSN online he pretended to be several different people that were: Josh, Monhour, and himself... he always used excuses why he typed at the same slow rate was because Monhour had his suit on and Josh is stupid. Now he straddles around cutting into conversations with my friends and friendships I've spent tireless hours cultivating, not to mention him stalking me. I walk away to the computer room excusing myself, five minutes later I see his ugly mug (He's not a very good looking lad) peering through the window to find me doing my assignment and then he worms his way in by sucking up to the teacher. I then go outside and he follows me AGAIN! I want to let him know I don't want him to be my friend ( What I've gathered is that he's using me to worm his way in to my friends circle 'My friends are guys' and using me because I'm a weak point) his name is Anthony, and he loves attention by making himself look stupid, he pretends his a super spy that creeps against walls, he never thanks me for anything, why does he lie about my life? he has no attraction to me at all and I'm the only one he's apparently told because I'm ' the same just like him ' that's bullshit, me and him aren't like eachother. I just want to know, how can I get him out of my life. Even if I piss him off he's going to make the rest of my life a living hell by destroying my friendship circle, I honestly and selfishly want to make him afraid of me, what he does is this technique he gets inside my head and says " Oh Meryl, you're that type of person the one that cares about everyone deep inside and you're outspoken " I DON'T LIKE IT WHEN PEOPLE ANALYZE ME, sorry but it makes me angry he also tries to manipulate me " What's wrong with you today? you're so emo today and Gothic " No I'm not, I'm just sitting down minding my own business, it may sound like concern but in his tone of voice he's trying to sweet talk me into feeling guilty. He tells me he can read what I'm feeling and that feels threatening, I once told him I don't believe him and he started treating me badly again... making me feel guilty, turning the guilt on me. I don't like it, what can I do about it? everyone likes him, they all think he's a strong person... I don't like it.