WOW, I am very sorry for you and all the others who are going through similar experiences. I don’t have any answers for you about how to bring your son back; I think different solutions work for different situations, and Hashem decides when the correct solution/yeshuo will come. You have to do your hishtadlus and daven. Professional help under the guidance of a Rav is certainly indicated.
Your son is 16; if you forbid the internet, he will very likely at some point access it without your consent. Don’t make it a red line.
I was a troubled teen a few years ago, I had reached a similar place as your son, and B”H am very involved in learning now.
“Back then” I wanted to buy my own computer. My father told me if I bring a DVD player or internet into the house, I could “sleep in the yard with my computer” because he wouldn’t allow either of those into the house. I did buy a computer and spent hours every night watching movies and browsing online, and was never asked to leave the house. I knew my parents didn’t like what I was doing and I knew they weren’t going to kick me out for those particular offenses.
I believe there is a spark of good in everyone, and an FFB kid who is rebelling has more than just a spark. The neshomo inside him can bring him back. It may take a while, but try not to escalate the situation, and then maybe he will allow the tenuous connection to grow into something more permanent. It happened for me. Also, focusing on the good in him will A) make your validation and acceptance of him more genuine, and B) help you to be more hopeful and thereby enable you to react with logic rather than emotion. You can use your recognition of his good points for yourself to give yourself hope that “me’at or docheh harbeh choshech”. With hope, you may find it eaiser to validate him and accept him.
If anything I wrote caused you pain, please forgive me; I am writing with ignorance of you, your son and your relationship with him.
We should all keep davening that Hashem should bless you and all of us with ????? ????? ???? ???? ???? ?????? ????? ???????