(((((((((Silver)))))))))
I'm so sorry you're experiencing this. I can relate to your situation: the screaming, the fighting, the physical abuse, being dragged into it, and even the guilt.
My mother was a wonderful person and I miss her dearly--the third anniversary of her passing is coming up on the 16th--but like all other humans, she had her flaws. She could at times be cruel, manipulative, and hurtful towards me and my father (though he was and still is a major source of conflict). I feel guilty even typing this, so I definitely know where you're coming from. You don't need to beat yourself up for telling the truth and expressing your feelings. I know how love-hate relationships can be so inredibly deifficult and emotionally taxing, but you have to make sure to love yourself--and your sister.
I am an only child. Drawback: I had to face the hell I faced at home everyday alone. But unlike you, I had nobody to protect except myself. Keep yourself and your sister safe; the hurt that your parents bring on your family is their fault, and their fault alone. You're doing the right thing, and I respect you for it.
With much love and support,
J