Ive been following this from the begining and I see you are tearing you hair out over this.
And ive seen nothing has really changed over the last 5 months. For whatever reason he doesnt want to be religious at this time in his life and I dont think at this juncture you can change that, thats why I think you need to accept it. It really could be alot worse, What if you son was really sick and there was no hope, At some point you would have to accept it as well.For your own mental health.
You need to accept for your benefit, not his. You need to decide what you want to do, Do you want to throw him out and accept the consequences of that (It might sound good now, but in 5 years you might feel very differently). It might entail disowning your son. he may never speak to you ever again. I see people say “Tough Love”, well tough Love doesnt always work and does backfire.
Do you want to let him go his own way and accept those consequnces that he might influence your other children to also go their own way, Maybe the neighbors will also disown you as well for this choice.
I dont think Therapy for HIM to become religous will nessasily work either. Some people just have a bad experience and its best for them to go away for those things to heal themselves. Maybe he had a