Keep in mind I will be 19 (legal adult in terms of residency) by the time I apply to UCSB, so wouldn't I be able to establish residency on my own?
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Establishing residency for STATE purposes is NOT the same as establishing residency for instate rate purposes in the state of Calif.
People from all over the world move to California. Having a degree from a California college does not give you a leg up on anyone getting a job there. People in California know UA, especially when the Tide cleans USC’s clock in the first game in September 
As the father of a soon to be freshman heading from the SEC country to the UC schools in the Fall, I have a few perspectives that may or may not be of value to you.
My daughter is starting UCSD honors program in the Fall. She is from Georgia. She was also accepted into the UGA honors program. Both good schools. Most would argue UCSD is better overall. Difference is that in Georgia, we have a program called the HOPE scholarship, where all profits from the GA lottery go to fund scholarships for GA high school kids who excelled in high school and choose to attend GA state colleges. I don’t recall the exact numbers, but it is something like all kids with a 3.5 high school GPA or higher gets 75% of their college tuition and room and board paid as long as they maintain a college GPA of 3.0 or higher. Kids with 3.75 GPA or higher get 100% paid. Again, I know I probably have these numbers off a bit, but that’s basically the deal. This program is what has escalated UGA and GT so far up the national rankings over the last 15-20 years.
But for our family, the choice was $63k+ for UCSD vs less than $10k for UGA (close to free.) For other, personal reasons my daughter wanted to get out of the south, and we are fortunate enough that we are in a position where we can financially support that, so she is going to UCSD, but there is no way that I believe that one college’s undergrad degree is $200k better than the other.
We too tried every way possible to skirt the UC out of state rules…it’s not possible…can’t be done. My recommendation - and what I would dictate to my own daughter if not for the aforementioned personal reasons…go to the cheaper, but still good school for your undergrad. UA in your case, (And yeah, if you call Alabama “AU” to an Alabama fan you might be burned at the stake
Have you run the NPC on some private schools in CA to see what your cost of attendance would (approximately) be?
There are some really good private universities and colleges in CA, along with those you’ve mentioned.