Why not ask an adviser? They know the ins and out of the curriculum and how to blend your interests and abilities with available majors and minors. You don’t need a formal minor in Accounting; but if it’s something you like and are good at (and A’s indicate that you are good at it, even if you did work for them), it might make a poli sci degree more marketable.
Yes, law school is a tough admit, and is quite expensive. Not a decision you have to make now, so why not just see how things go this year?
One last thing, and I mean this kindly: It sounds like you aren’t very confident. That’s almost refreshing after reading posts from students and parents who are way over-impressed with themselves–but you’ve achieved a lot already, and UCSD is a good school where you would not have been admitted if you weren’t qualified. Maybe the path you’ve taken so far is a little circuitous, but that’s OK. Besides working with an adviser to get your academics on track, maybe a visit to a counselor at school would be a good idea, someone who could help you focus on the positive aspects of your life and education. I wish you well.