My Boyfriend Got Raped By His Step-father, Both Sides Of Family Are Abusive

Hello. My boyfriend(15) is from South Carolina, I'm from Europe. This isn't the first time. I wanted to call CPS or the police, but he's afraid his real father might sue his mom for not protecting her child. She doesn't know about the abuse though. There are guns in the house so there is a risk that if he tells anyone he might be in danger. My boyfriend is a transgender male(please don't be transphobic in the comments, this isn't what it's about) and can get pregnant. The risk isn't high as he has an eating disorder but he still gets periods. He cannot get a plan b pill, it costs too much and his mom would know he went to a pharmacy from the tracking app in his phone. I really don't know what to do, this is a terrible situation and I need legal advice. Is it possible for his real father to actually sue his mother if she didn't know about what's happening? Is there anything I can do, other than support him emotionally? I don't want him in danger.