Please-we need help

I wasn’t sure where to post this & need to stay anonymous. My son has a lot of problems & we needed to hospitalize him when he was 9. He came home MUCH worse than when he went in. He was severely angry, began wetting the bed/smearing poop on the walls & saying very inappropriate things (none of these things were EVER an issue before). Almost 2 years later he told us that he was repeatedly raped by a male staff member while he was hospitalized. We called the police, there was an investigation & after everything they were not able to locate this man. We have done everything in our power but at this point it’s been 5 years. He is in therapy 2x/week with a wonderful therapist but nothing is helping. It’s all he talks about. He blames us for putting him in there. The guilt & depression I feel is overwhelming. Tonight during one of his rages, he physically came after me. (He’s a big kid 6’1 & 190 lbs.) My husband got between us & he punched my husband in the nose. My husband hit him back. He told us that he is going to tell people that we raped him & he will destroy our lives for not doing more to get justice for him. I am PETRIFIED. I don’t know what to do. We have 2 younger children. I’m just beside myself right now. Can someone please give me some advice? I don’t know what to do. We live like prisoners in our home. I’m constantly taking the younger kids into the laundry room and locking the door so they won’t be witnessing him punching holes in the walls & the things he’s saying. Obviously he should be hospitalized but we feel like we can’t do that again and he knows it, so we’re always at his mercy.