What do you plan to use to study physics? I recommend physics for scientists and engineers by Randall Knight.

(1) Look at potential 4-yr universities that you would be interested in. Look up their bachelor's programs in, e.g., physics and aerospace engineering. Speak to an advisor at your current school. See how the courses at your current school would map into the programs at the 4-yr universities.

(2) With respect to a potential physics major, if you will be graduating from your current school without any college-level physics courses, I don't see how you can enroll in a 4-yr university as a junior. Many majors (such as physics) have a strict prescribed sequence of courses. If you haven't taken equivalent college-level freshman and sophomore physics courses at your current school (if I understand you correctly, they aren't even offered there), then you would have to complete that sequence at a 4-yr university before continuing on to college-level junior and senior physics courses.

(3) It does appear that at your current school, you can complete college-level freshman and sophomore math classes (but you may have to pay extra). Assuming you can transfer these credits to a 4-yr university (confirm!), that would be worthwhile, even if you do have to pay extra. You will need these math courses for physics or engineering majors anyway, and it's better to take them in advance of, rather than in parallel with, the physics and engineering courses. If you take the math courses at a 4-yr university, you will be paying for them anyways (from a financial consideration, check how much you will be paying at your current school vs at a 4-yr university).

(4) It's not a good strategy to choose a major (such as aerospace engineering) strictly based on what is hot in the job market currently. As I've posted many times before, job markets can invert in a year or so. Sometimes dictated by advances in technology; often dictated by changes in government policies, regulations, and funding; and often dictated by the latest fads taught in business schools. You are at least 4 yrs away (and a lot more if you pursue a PhD) from entering the job market.

(5) If you do pursue a PhD in physics in the US, you typically do not apply for a separate master's first.

(6) Given your situation, even if you don't enter a 4-yr university as a junior, you will likely receive some credit for gen ed and math courses. That gives you freedom to take more electives and, perhaps double major, e.g., in physics and engineering (of some sort). At this point, you've stated that an intended major in physics or aerospace engineering won't affect the program in your current school. So, when you do enroll in a 4-yr university, try out physics along with various engineering courses and see what sparks your passion.

One advantage of a double major in physics and engineering is that you can seamlessly decide on your graduate program (if any). If you choose physics, you really should go the PhD route. But with most branches of engineering, you can stop with a master's if you so choose. Even if you do go the physics route, the engineering background will be advantageous should you choose to be an experimentalist, rather than a theoretician.

You can expect to take 120 credit hours, which usually translates to 40 classes or five per semester. You say you are now taking four classes per semester, which can cover the core curriculum if all courses are transferable. So make sure they are transferable. But it leaves little time for major courses that would have been taken in the first two years.

If you enter as a junior, you will probably be taking five physics/ engineering/math courses each semester, which is a load. In a normal four-year program, you would probably only have taken four major courses.

Finally, how are you handling your current program? Remember, university is a notch up from the effort that a usual HS program requires.

Good Luck