Look, regular high school is one of the most vicious places for a person with anxiety. Horrible horrible enivoronment. I don't blame you for wanting to leave. I also get a sense that are one of the "enlightened" ones who realize that everything you're doing in high school is actually pointless; and indeed you are correct. It is pointless....
I think you want to get the high school degree however, that's one thing that'll help you out in the long run... A lot of people can get by in the entreprenuerial world, or career world with a high school degree; very few succeed without the bare minimum.
There are charter schools, alternative schools available which I would look into if at all possible. Otherwise, I suppose as horrific as it may be roughing out traditional high school might be worth it. You already have spent so many years to get to where you are.
And either way get therapy. It will help.