Welcome zba. You surely have your hands full, don't you? At this age, it's anyones guess as to what is going on with your difficult child (gift from god - the child who brought you here).
Now is the diagnosis merry-go-round. Whether medications are indicated or if there's something else going on. A parent can lose their mind trying to keep up with this & run their household. I hope you have a psychiatrist you trust; it's also recommended that a complete neuropsychologist evaluation be performed. (It's perfect at this time while he's in Residential Treatment Center (RTC))
As for bringing difficult child home from Residential Treatment Center (RTC), there should be a discharge planning meeting to include the crisis interventions you may need for young difficult child. The behavioral model will depend on difficult children diagnosis, his personality & general demeanor. It's all very individual & can take a great deal of time to put together. I have twin difficult children; 2 entirely different needs in parenting.
In the meantime, take this time to recharge, research & be ready for discharge date. With my adoptive children I've stayed away from the explosive child because of their hx in the birth home - instead I used the love & logic books. It's all up to what you can handle & what your difficult child will tolerate. Please know that you're doing a remarkable job with your difficult child if he's already in a treatment facility. It takes many of us here years to advocate to that level. Our mommy hearts get so torn by this.
Take care of yourself & keep us updated.