Update 2 - (Trigger) Abuse by SS14
Just to update you all who have been following along.
DH continues to blame me for this entire mess, and believes that SS is innocent. He believes that LO4 lied. He has been attempting to make life uncomfortable for everyone - continual snide remarks, interrogations, waking me up early to talk right then and there. I largely ignore. It's not worth having the same fight with him or even engaging this loser of a man. SD18 is taking this whole thing personally, and has been rude to the rest of the family. Because everything inevitable is about her. Fortunately, she has been spending most of her time with her Mom. She returns to school soon, thankfully. For a while we thought she was going to fail out but she fortunately made it through and will be gone in a week.
We have an appointment for LO4 with a therapist (next week) and it can't come soon enough. This past weekend, I negotiated with DH that he would take SS and SD away so that LOs and I could stay home. SS14 is not scheduled to be back at our house for two weeks. This gives me enough time to get the rooms switched (SS's room will be downstairs in the finished basement), and the door alarms and cameras installed. The door alarms are small and discreet. The cameras I'm still deciding on but I will get something installed before SS returns. And hopefully, the therapist will suggest that we maintain separate residences for SS and LOs. But if that doesn't happen, or if DH still fights it, I need to maintain separation, security and constant supervision in the home.
DH is having a hissy fit over the need to switch rooms, because it might seem to SS that he's being punished and that SD will lose her ensuite bedroom-bathroom. I rolled my eyes at his little fit. The room switch is happening. I told DH that if he doesn't help me move everything, I will hire movers to do the lifting up and down the stairs. I just can't even with this guy.
My mother has been coming on the weekends to back me up and my father gave DH a lecture. They both told DH that they would be watching SS and ensuring LOs safety, since he was failing to make that a priority as their father. So, now DH is going to be stuck with his mother-in-law, at a minimum, every time SS is in the home (and that's assuming that we don't make other provisions for SS).