My sister lives in Georgia too

My step mom pulled that same quilt tripping crap, saying that I was a bad influence to my younger brother and others, and that I was the 'daughter she never had ' feh. Ignore it. They're trying crazy rationalizations to convince you that you don't need help, which is both selfish and ignorant. She also told me that I was too young and impressionable to know who I really was, or what was good for me (I'm almost 21).
Don't drop out of high school! As long as they ask for it on an application, it's still relevant. Go back and finish, wait until you're on T/ change your name if that will help. If that takes too long, go get your GED. I know that I sound like a nagger but it's the truth, I know. I used to abuse substances too. I've drinken a lot when depressed, taken prescription drugs (they were given to me fair and square, but I didn't need as many as the doc gave me, so I took them unnecessarily to get the high). That stuff is a great distraction, but when you wake up in the morning with a hangover, your problems will still be there. You'll die of liver disease before you drink your problems away. I'm really glad to hear that you've been sober for so long, good for YOU!
I dealt with the same negativity for years. Just be strong, get a job, move out. Heck, get emancipated if you have to. There were no groups where I lived either, so this site was my only solace to ask questions and post posts like this one. I ended up moving 100 miles from my parents in the end. I hope this helps, at least a little.