You say you are feeling trapped because he will be on the street without you. Hon, that is what he needs. He needs to stand up on his own two feet, and not rely on having a soft place to land. There are options for him. There are shelters, and the salvation army. And probably he has friends who would let him stay a night or two while he figures it out. He existed ok before you go together. Trust me, telling my AD that she could not live at home anymore, knowing that she would just go live with her drug friends in a place less than sanitary and safe was one of the hardest things if not the hardest thing I ever had to do in my life. But my home has returned back to a home, and at the end of the day it is a soft place for ME to come home to.
Go to some AlAnon meetings, tell him to leave, change the locks, and save your sanity. If he is doing crack, you can bet that sooner or later when you aren't at home, there will be someone else in that house doing it. Things will also start disappearing.
Much love, cuz I know your in a hard spot to be in.