All colleges (especially very selective ones like USC) will tell you that you should take as many challenging/advanced classes you can handle. They like to see you have a rigorous class load and are challenging yourself. If you can handle the rigorous load, then they know you are ready for their school. Having said that, what you don’t want to do is overload yourself and end up getting bad grades. Between getting a B in an AP class vs. an A in a non-AP one, they tend to favor the former, as you have shown you are challenging yourself. Of course, getting an A in an AP class is even better!
As for the foreign language, two years should be fine. My kids’ high school recommend at least two years for selective colleges and the US News website said USC recommend 3 units (a.k.a. 1.5 yr).
As for the BFA program, please know that USC BFA program is quite different than other colleges. I just attended a informational session with my son last month. They just completely revamped them. It is different in that you will taking the exact same classes with the same group of people for four years. You will not have ANY (or very little) electives. The BA program, on the other hand, is much more open. Before this session, my son has applied to only BFA programs and has no interests in any BA ones. However, after listening to their pitch, he decided to apply to both at USC.
Now, here is the kicker (as far as I understand). BFA is mostly about the audition. For quite a few schools, 80% of the decision is your audition. As long as you get decent grades, they will accept you, no matter what classes you took in high school. For schools with an academic reputation (e.g. Carnegie Mellon, USC, Syracuse etc), you will still need to get past the audition, then it is up to the admission office to decide who to accept based on a variety of factors (grades, course load, test scores, diversity etc). Every school admission process is different. For example, Syracuse said they give a grade for each applicant that auditioned (e.g. 100, 90, 80 etc). Then they sent the pile to the admission office. The admission office then take the 100s and look at their academic profiles. If one of them also has a 100 on the academic profile, he/she is in. If the applicant has a poor academic profile, they might put that person aside for later consideration or outright deny him/her. Then they go next to the 90s and so forth until they have the necessary acceptance pool. Not sure how USC does it, but this gives you an idea how it might work.
The BA program, on the other hand, is like other majors. It is based on your academic record as there is no audition ( what classes you take, extracurricular activities, your ACT/SAT scores etc).
Lastly, if you want to major in theatre, then you should take classes in theatre, participate in your school or local theater productions. It looks like you are already doing that. Just like if you are going to major in engineering, then you should be taking rigorous math and science classes and getting involved in robot club etc.
Hope this helps!