Need help with university applications :(

You have a great profile from what I understand of international grading systems, and you have plenty of extracurriculars they will like. In order to apply smartly, I wouldn't consider any of the Ivy Leagues or Stanford your "target" schools. Consider all of these reach schools. Remember for top tier schools you will usually have to interview as well, so stats alone won't get you in. Also, thousands of extremely talented students apply to these schools from around the world and within the US every year. The acceptance rates are below 5%. So definitely apply for those as reach schools but for your own good, please apply to other schools as target/safety. You could consider prestigious state schools, like the some of the UC system schools or NYU, for example. Additionally there are other high ranking universities that are not designated as Ivies but are still prestigious. If your dream is to study in the US, you should be prepared for the possibility that it might not be at Stanford or an Ivy League.

Your ECs are very good, but very good is the norm when it comes to international Asian applicants. You have a chance at the ivies/stanford, but there's no guaranteed admits anywhere, especially if you need a lot of aid. E.g. high-need applicant I know got rejected/waitlisted by 14 schools, and got into Caltech for engineering (finaid hasn't come through but it'll be full).

To answer your question better I'll need to know what your efc is, to be honest.

I come from a very middle class family with my mother being the single breadwinner. Hence, I have to get atleast 80% scholarship. I plan to take out student loans for the remaining tuition (or if I do not scholarships) I have to pay since I don't want to put financial pressure on my mother. If needed, my mother can contribute about 20K USD.