Wow, your son sounds a lot like myself. I was also the oldest of 3, started playing ice hockey at age 8, and probably also acted out a bit at that age, for the same reasons. I mellowed out after a while, but 13 may be just the beginning of a long ordeal with rebellious tendencies.
I think parents tend to sometimes unfairly expect more out of their first child, and build up some extra pressure there, when it isn't needed. Teenage kids have enough pressure these days as it is, and I believe that overbearing parents (not to say that you are one) can contribute to this effect, causing the pot to boil over on occasion. Giving him space, while remaining supportive, and not expecting him to be "perfect" (whatever that may be), I think is a good path to take.