Awesome thread mate, keep it going. I went to college not uni and started working properly at 16. You don't need uni or college even, don't listen to that shiz. You've already made a career by 15, so just think about your schoolmates who will finally be looking for jobs at 23-24 after uni, with a degree up their arse, but no life experience.
You're in an awesome position. Keep it up, keep varying it, keep protecting yourself with new/other ways of making money and you will never regret it. Circumstances and people will try and bring you down along the way but always keep fighting and moving forward. Don't look at it as 'some prick did a chargeback' just look at it as a refund. A faceless customer who didn't like the product. It happens, even if they were trying to scam you, shit happens. Move on. Have some 'float' in your PayPal for such times and run your business - take a % as a wage, not all of the profit. I know you have your goals before Xmas, but cash flow is imperative for chargebacks, new stuff, new ideas, costs etc etc.
I'm totally in awe of you. I wish I had the confidence to do what you're doing at 15 but the Internet wasn't even available to Joe Public when I was 15 LOL.