This might be one of the first things that I noticed. You are very young. You have quite a bit of time to think about this.
Stanford and many (or perhaps most) of the schools on your list are need blind for admissions for US citizens (and permanent residents). Thus your need for aid will not impact your chances of admissions. Being URM will help your chances. Even with this, all of the schools on your list are reaches for nearly every strong student.
One thing that can be a challenge is to determine what level of academic rigor is comfortable for you. AP and honors classes are tougher than regular classes. Some of the top universities (Caltech and MIT particularly come to mind) are academically very challenging. It is hard for any particular student to know whether this is a good fit for them until they try it. I think that all strong students just have to figure this out over time.
I got my master’s degree at Stanford. By the time that I got there, I had two years of work experience (after getting my bachelor’s degree) and I was very much ready to work as hard as was needed at Stanford. This did include doing quite a bit of homework over the weekend in addition to week nights. I still remember very well spending 6 hours on a Saturday solving one problem (out of 5, for the homework of one class out of 5) and loving it. Not everyone loves spending Saturday 11am through 5pm doing homework. Again, we each need to figure out what is right for us. Personally I loved the time that I was there.
In terms of extracurricular activities, and in terms of which classes to take, I am a fan of figuring out what is right for you, doing what is right for you, and doing it very well. What is right for you, what is right for me, and what is right for someone else might be three entirely different things. The “applying sideways” blog on the MIT admissions web site seems to recommend this same “do what is right for you” approach, and I believe that this applies for other top schools in addition to MIT.
And taking care of foster siblings is an EC. This shows responsibility and the ability to put in the effort and do what needs to be done which are valuable skills when you get to university.
To me it sounds like you are doing very well. Take this one day at a time, keep ahead in your work, and you should do well. You are however young and it is hard to chance you for top schools until you have results from the next two years of high school.
Also, if you can then take some time to think about what you want in a university. The highest rated universities and LACs do differ in some significant ways.