Ethan, I just posted something that can help answer some of your questions.
I don't think it's too late for you since you are only 16/17. However, my conversation with our HS coach yesterday was that he would ONLY select kids that could help him win games. With that being said, you are only looking at two more HS years at most, and I really don't know your skills, or you will make the varsity team. But I would encourage you to set a goal and work towards that goal!
Yes, you will need to develop other pitches in order to be "more" effective. Learning new things is part of the fun.
Best luck to you.