He doesn't have to choose the street, Windblown, he could choose the Salvation Army Rehab which is free, he could choose going to meetings and connecting with other clean and sober people who could maybe connect him with housing or Sober Living.
"We" are not the solution, but if we interfere enough "we" can become a big part of the problem. I did and I was for too many years. When I knew better I did better.
Keeping you both in my prayers. Hubby too, just because he disagrees with you doesn't mean he doesn't love your son as much as you do, he's just seeing it from a clearer perspective. My hubby did too and he was right.
Hugs