Options
I'm very sorry to read of your experiences and of the situation that you're in. Reaching out is a clear indication that you have every intention of "Doing Something" to emerge from this. There are options available.
Sadly, the legal "age of consent" is 18 and we can't alter that legal fact. Having typed that doesn't mean that you're in a hopeless situation. It's just going to take some seriously courageous steps on your part - and, only you can take these steps for yourself.
The first thing that I would do would be to contact my local domestic violence hotline, or
http://www.thehotline.org,
and speak to an intake person about my situation, abuse, and the abuse of my siblings. By contacting this agency, I would be put in touch with a network of support and assistance, as well as my siblings.
The second thing that I would do would be to engage in some strong counseling therapy THROUGH the domestic violence hotline resources - just because I would be 19 does not mean that I'm "too old" for help, on any level. If I were enrolled in college, I would still be considered my mother's "dependant" and she would be responsible for seeing to my well-being.
The third thing that I would do would be to reach out to all of my family members and ask for help for myself, and my siblings. I would try to keep in mind that I am NOT responsible for the care and well being of anyone other than myself, including my younger sibling and older "special needs" sibling.
Having typed all of that, I would encourage you to contact your local domestic violence hotline, ASAP. I would also strongly encourage you to (as much as I hate to suggest this) contact Social Services, ASAP.
Where is your father in all of this - I didn't see a mention of his involvement in your life. Is he paying child support for your other siblings? If so, he has a right to know what sort of environment you're all living in and, if he is at all conscientious as a parent, he will file for custody of the other siblings and do whatever he can to assist you.
In any event, you DO have options. Taking the first step is the hardest one of all, but you don't read like you're prepared to give up, just yet. You're young enough to recover from your childhood experiences and develop into a successful and productive adult. You have the ability to do this. It's just a matter of taking the first step.
http://www.thehotline.org
My very best wishes to you.