There are a couple of things that stood out to me.
Since you’re a “bit young”, you would probably do better applying as a repeat 9th grader. Also, I’d be very wary about trying to jump ahead in the math sequence so much. You run the risk of being bored in your regular school math classes and developing holes in your math understanding.
Also:
Do proofread your applications. That would be the one thing that may have got you waitlisted or rejected. It showed that you weren’t very invested in applying to the school. Don’t contact the orchestra teacher unless prompted by the admissions officer.