Hi. I noticed you did not get a response so I will do my best. I am sorry you are dealing with this. It is hard!
Unfortunately there is no answer to your question. None of us control anyone else no matter how hard we try or how much we love the person. As you found out, even providing shelter and other help does not make them grateful or willing to get go for treatment. We did that too. My daughter is still out there way on the other side of the country. Some people eventually decide to get better. That is up to your son. Only he can do it. Or mot.
The one person we can control is ourselves. We can get the help that WE need (and we do need help) and start doing the hard work we need to do in order to learn to live a sane life, even though our adult child is off the rails. Most of us are working hard to detach with love from the chaos. Some of us have therapists and some go to 12 STEP meetings for codependency or they attend Families Anonymous. YOU can join a 12 step group that meets on a Zoom. I do that. Look online for information. The solution for most of us is to learn these self help skills. I went to therapy and to online NarAnon because my daughter uses drugs. They saved my marriage for sure and maybe my life. No exaggeration.
in my opinion this is too hard to do alone and I never heard of any parent being able to save a grown child by doing everything for him/her. That makes them feel helpless.
If your son is a danger to himself or others then and only then can and should you call the police so that they can take him to ER. There he may or may not be detained for a few days. Other than that, your 24/7 worry won't help him at all and may impact your own health. And you are important. You matter.
I hope this helped a little. We all get it...we were all there at one time.
Hugs and prayers!!