The deportation makes me super nervous because it's like he has nothing to lose anymore - he is already going to lose his family if he gets kicked out. Do you think she is in serious danger? Would he kill her or the baby?

I just went through this a month ago with a friend whose bf was cooking meth in her apartment and who was threatening to have her evicted if she tried to get him out. She called me and a few other people for help. I did what I could, short of calling the cops, but it was all useless because she kept letting him back into the place. I finally told her that what happened was up to her - I couldn't do anything else until she decided what she wanted to do.

Your sister doesn't even want him gone at this point, so it's even harder for you. You can really only be there for her if she asks for your help or needs it.