How to get my younger brother away from my mom?

My divorced parents have split custody of my younger brother. My mom has 52% my dad 48%. I think. I NEED TO GET MY YOUNGER BROTHER OUT OF THE HOUSE.

Either way I recently was kicked out of my mothers house, Which turned out to be good, she was allowing anything to go on in her home. By me, her boyfriend or friends. I think she is addicted to drugs.

While I lived these all happened:

Everyone smoked pot

Moms boyfriend , when he would live there for sometime, would drink all day, never have a job. Mom has told me he smoked crack. he busted down a door in the apartment trying to attack my mom.

The boyfriend was stabbed by my mom friend for starting a fight.

Cops were called on the house numerous times, At least 5 different times.

He punched my mom in the face and she had a black eye. And she would still allow him to come back.

Things I know my dad doesn't know:

My mom and her boyfriend. Smoke pot a lot. Drinking everyday. And its not a fun environment they use so much they are reckless, emotional, and want to fight.

My mom has some kind of drug charge in another state.

I am so scared for my younger brother, I am so mad myself for not doing something to this horrible guy and my mom in the first place.. now my younger brother, the only person I really love is going through it. He is only 12 years old and I know he is being hurt going over there.

I know my mom brainwashes him and makes him feel like my dad is so horrible and its all my dads fault that she is stuck with a bad job and can only afford and apartment on food stamps. They divorced more than 10 years ago. My brother can not do it himself , I know for a fact it is not safe over there, and he will be much better to live at my dad full time.

We all live in a great neighborhood. My dad has a great awesome girlfriend hes been with for 3 years and they never fight. They always treat us good and will always help if we needed anything.

Please someone help me.