In order to get back to your normal self, you will probably benefit from starting a mood stabilizer. It might be able to reduce depressions in the future, making the Zoloft less necessary. Getting back to genetics, no one in my immediate family has bipolar, but two generations back there's quite a history of mental illness. A couple of different bipolar people I know claim marijuana helps them remain stable. It is known to increase the likelihood that someone will be paranoid if he or she becomes manic.
Nobody knows the extent to which long term antipsychotic treatment is helpful in bipolar disorder.
Since I'm bipolar, I am concerned about him. By his age, bipolar disorder starts looking more like it does in adults. Unlike general adolescent storminess, mood disorder symptoms could impair his ability to function in school etc., and are likely to have something of an episodic course. In individuals, yes, but not as a general pattern. Prozac can also cause sleep difficulties.