IMHO your first priority is to save your other kids. They need you now, emotionally, spiritually, and physically, more – not less – than before. Saying that something is unacceptable and then accepting it is gornisht verd. Find out what the law is about taking care of a 16-yo truant. If you provide a place for him to stay and pay for it, did you do anything illegal? Don’t give him leverage to threaten you with. If he wants to stay home (which shows that you’re doing something right) use it as leverage against him! If he doesn’t find a school or a job, or his behavior affects his siblings, out he goes.
My heart breaks giving you this advice, but I feel achrayus to mention it because someone told my husband he has an OTD son and everyone told him to keep him home, and it had a terrible affect on his other kids. May you have only nachas from all of your kids, ????? ?? ???? ?? ???? ??? ???? ?? ?????.