I've been where you are many many times you are not alone. The many here responses prove it.
Your post shows you've got a good grasp about your sons illness.
Our sons commitments and hospitalizations (especially with police involved) were traumatic frightening heartbreaking painful visceral experiences. When our un medicated son became more threatening we tried desperately to keeps things stable. Looking back I see that trying to mange our sons worsening condition at home was an impossible situation. His initial physcotic episodes combined with the substance abuse had to reach a breaking point before we could get him into treatment.
He's sat in an er for almost a week waiting for a bed,
After one assault early on he spent the night in the county jail.
During another episode he ran off from the hospital ER in October barefoot with only a gown and spent the night in the woods. I'm sure many of those reading have been through similar experiences.
This was all with both my wife and I working to keep things sane. An unsupported caregiver has a much larger challenge !
My suggestion is go to your local magistrate tell them whats happening (with as many specific details as possible) and let them know you want an involuntary commitment. Request CIT trained deputies if they have any.
Next time you're threatened call the police they should come out, pick him up and transport him to a hospital. Prior communication with the police about the IVC will help deescalate a scary situation.
Once in the system he can get treatment. It may take time to find a bed, there could be other issues but once it commitment happens you can get some rest knowing he is safe you are safe and an opportunity for improvement has opened. We've through several hospitalizations but eventually he gained more insight into his illness and became more stable. If you need to tell the social workers/case mangers you are unable to have him at home they should work at finding housing. Looking back I also feel like our son got a message about how we would react when he was out of control. Perhaps you've heard all this already but you are absolutely not alone.
Tears, grieving ,therapy and a psychiatrist all continue to help me with the enduring sadness that is part of this terrible disease. Things are better now but its taken many years. Hang in there.