I think that you should read the “applying sideways” blog on the MIT admissions web site.
As I understand it, it recommends that you do whatever is right for you, and do it very well. This approach has worked very well for us. However, what my younger daughter did, what my older daughter did, what my wife did, and what I did were four very different things. We each did what was right for us. I guess the common thing that we all did was to take education seriously. However, in terms of ECs we mostly did different things.
And look for universities that are a good fit for you, pay attention to your budget, and make sure that you apply to at least one and preferably two safeties. U.Mass Amherst looks like a very good safety for you assuming that you keep up your excellent work and continue to be in-state in Massachusetts.
Exactly right!
And here is the blog:
Also, to me it looks like you are doing very well right now.