<p>I think you are pursuing all the correct avenues. I’d like to emphasize the importance of music theory, probably over voice study at this point (unless voice is going to be an important part of your musical studies–I notice you are very involved in choral groups). For theory and composition, piano is probably the most important instrument to learn and knowing piano helps get the theory to where it needs to be. I am guessing that from all the choral work you’ve done, you have the necessary vocal musicianship skills for Berkelee’s audition.
If money is not a problem, I would follow the good advice suggested here about summer music programs. Boston University’s school of fine arts is another possibility in addition to music festivals and would put you in proximity to Berkelee School of Music. You could make contact with teachers there over the summer in composition, voice, etc. and get to know the students.</p>