I also believe that you have two addicts in your home. One hidden under the blanket of a prescription drug user, the other a street user.
If he has overstepped a boundry, then you need to follow through, and, he needs to leave. Set a realistic date, like 2 weeks then he must leave. He is an adult, allow him the dignity to find his own way, to hopefully learn to become a responsibile adult.
As for you, meetings, meetings and more meetings, your recovery first. There needs to be one healthy person in this family, tag, your it!
Keep posting we are here for you.