You are certainly in a difficult situation. I agree with therapist - stabilization first. Safety first.
in my humble opinion, if it takes medications for your difficult child to make safe choices & use non aggressive reactions I'd go that route. (Have with both of my children - not an easy decision but one I've had to make to have a level of safety around here.)
Let go of the "diagnosis" for the time being. As your difficult child is being tested; as medications are added or decreased & stopped the diagnosis will slowly shine through. A treatment plan will all of a sudden become effective. Given this is mental/emotional illness this is not a hard science. There isn't any one test or indicator of what may or may not be going on. That is the most frustrating part of this.
by the way, I don't say what I've said off the top of my head. I remember one day telling psychiatrist - "call her pregnant, just treat her". This was after an ER admit & we were trying to get kt safely off the ceiling. The top ER doctor walked in & I asked him to "bomb" kt. Tranq her so she is safe - this level wasn't good for any of us. We could work out the whys & wherefores later. He agreed.
(((hugs)))