Write or wrong–how is your son doing?
I havent read through all 43 pages of this thread, but does he do drugs? If that is the case, an enormous step towards coming back is stopping that. Even if it is something as relatively innocuous as marijuana( I am not saying it is not bad, and in fact am very anti it, but comparatively) completely changes ones outlook. It is near impossible to take life seriously if one is using drugs.
Also, just an idea, show him some of the “cooler” sides of the torah. I.e, the juggler and the king, Maharal’s beer hagola. Seeing torah as something enjoyable can really change it around completely. This obviously depends on his personality type, what he is into intellectualy, and if he is even willing to read something “jewish”.
Also, I know this has definitely been said multiple times, and it is obvious from here that you are a loving, caring parent, but he needs to see that he can be open with you. Show him yourself as anything other than an authority figure.
I wish you the greatest hatzlocho, that Hashem should bless you abd your family, and should help your son through this patch of his life. I hope that what I said can be of some use to you, if not, just know that there are many of us thinking of and davening for you and your son. May we hear only besoros tovos.