I often find that people who claim to be able to "Kick your ***" oftentimes can't and are just using that threat as a way of gaining control over you, however little it may grant.
all you can do, until he actually attempts the ***-kicking, is find the flaws in his verbal abuses, throw them back at him and tell authority figures what's going on.
If he approaches you menacingly, with a clear intent of starting something (clenched fists are a popular cue, as is a dragonball-z-esque-furrowed-brows glare)it is often best to strike quickly, and so that he won't be able to fight back easily. A quick jab or backfist to the nose is an optimal attack for this. if his friends have any mental capacity at all, they'll notice their buddy dropping, and figure it best not to agitate you further.
HOWEVER. Strike only after exhausting all other resources. Tell teachers, parents, adults, etc. Alert anyone in power that there may be a conflict and, although they probably won't do anything, you can use that to avoid trouble, simply because you TRIED to avoid it.
hope I've helped.