The first thing that occurred to me when reading your post was the “applying sideways” blog on the MIT admissions web site. @tsbna44 posted a link before I got to it. As I understand it, it recommends that you do what is right for you, and do it very well. This sounds like exactly what you have done.
One recommendation would be to just keep doing what is right for you, and keep doing it very well.
A second recommendation would be to pay very little attention to university rankings. Instead look for a university that is a good fit for you. Of course this means that you need to think about what “a good fit for you” means in your case.
And the third recommendation would be to pay attention to your budget, and make sure that you apply to safeties. Schools in the Ivy League are not safeties.
In terms of GPA calculation, different high schools in the US do it in wildly different ways. Here on CC many of us prefer a calculation based on A=4.0, B=3.0, C=2.0, D=1.0, and F=0. Just add up the total number of courses in each category and find the average.
And I think that you are doing very well up to now.