Ice cream? Shoot, I would have taken you out for pizza. But I hear ice cream's better for this kind of situation, they told me long ago that ice cream's the best thing after getting your ears pierced (I am never getting my ears pierced again).
What you did was show the bully that you're not going to take his junk anymore, and that you'll fight back if he does it again. Now you've got your friends' respect and you've got your dad's respect, and even the bully respects you now to some degree.
I do believe in nonviolent negotiation and peacemaking, but there are just some situations where the only thing a person will understand is a punch to the face.
If your friends were around, then you should have enough people to back you up in case the principal threatens to suspend you. I had a math teacher once who explained at the start of the school year, that if you put your muddy boot on someone's back in class and they turn around and beat the snot out of you for it, he's not going to do anything about it because you brought it on yourself. Of course, he was from the old school, the new school is a lot different...
It should be the teachers' or faculty's duty to prevent this kind of stuff, but if they know it's going on but choose to do nothing, then I still don't advocate martial law but shoot, the kid's bound to get it smacked into him sooner or later that treating other people like punching bags just isn't suitable behavior.
That was basically several paragraphs worth of "you did the right thing". Don't let whatever consequences the school hands you for it tell you otherwise.