Can my mother keep getting away with abusing my siblings and ripping our family apart?

[BigSister]

OK so I wont get into my life story here but I will tell you that my mother has abused me and my siblings a lot. And does anything she can to hurt us. I am 21 now and married, my sister is now 18 and living outside the house and my brother is 13 and still stuck with her. I will also tell you that she abuses drugs and alcohol. When I was still at home I tried to get Social Services involved and to believe me but no one would. Then they finally did when my mom tested positive in court for meth. But they did not take away my brother and sister at the time. About a year ago my little brother started getting abused by my mom very badly along with her new husband. He went to Social Services and no one would believe him and then they called me and asked me if I had heard what was going on and then asked me questions. I said yes and that my brother wouldn't make something like this up. I also told them that they were welcome to look at my files and it would prove a pattern. However since then I have not heard anything, and when I call they will not answer or return my calls and I am not sure where the case stands now. My brother is also struggling with school and I know this is the reason because I went through the same thing. The year I was with my mom I had straight F's and then when I was removed I was getting A's and B's. I also told them that me and my husband are more than able and willing to give him a good home and that my husband has worked for the government for 9 years and there for had a good steady job. Then my mom found out that Social Services had called me and that I didn't lie for her and now she has cut me off from my brother and tried to do the same with my sister. My sister and I still talk but we have to be in hiding about it which I don't think is right. And to give you an idea about how things are, she goes on my facebook page with her sister and makes fun of my posts and my pictures, and will take my pictures, copy and paste them and draw stupid things on them. And just recently she found out that I was going to be coming to town ( and I live 1500 miles away) and she put my brother on a house arrest for the whole month that she thinks I am going to be there, and I am only going to be there for like a week and a half. I didn't think this was fair and so I posted on Facebook that "oh man looks like I wont be able come to town after all." Hoping that she wont make my brother stay in the house for the whole month. Also I want to add that my sister, before she moved away had really planed her life out and knew what she wanted to do. So she moved out when she was 18 and moved to a town about 100 miles away and just now she has came back to this town that my mother lives in and is now abusing drugs and alcohol and has no plans on where she wants her life to go. I want to help my brother so much but I don't know what to do, I don't want the same thing to happen to him that my sister is doing. I have called Social Services and can not get any help from them and I talked to some lawyers that say its a 50/50 change if I take my mom to court for custody for my brother but that it probably wont turn out to my favor. Someone please help. Thank you for reading.