If this kid is saying what you've been telling us, he's going to fight dirty. That means you have to fight dirty as well or you're gonna get your shit rocked.
Be aggressive as hell, get up in his face, if you're close enough he won't be able to get a decent swing off. When you see an opportunity, grab him. Now you have some options:
You can knee him, that will put him out for a little while and you can walk away or beat the shit out of him, your call.
You can grab his arm, put it behind his back, and use your other arm to rail on him mercilessly. Good spots are the top of the head, the ribs, and the lower back.
Toss him on the ground, get on top of him, and hit him in the face. Once you're on top success is pretty much guaranteed unless he has a working knowledge of how to fight.
The other tips all still apply... the object behind thing, the sternum thing if you can manage it... my only concern is that if he's picking the fight, he probably has some idea how to fight, and you apparently don't. If that's the case, you're gonna get your ass kicked trying to straight-up box.