All of the above responses contain great wisdom. Please read them again and again!!
Would you allow any type of acquaintance in your home to treat you this way? What would you do if they did?
Meth is a seriously dangerous drug and no matter what, he would be FAR better off in prison than he is there where he continues to use. Every day that he continues, more damage is being done to his brain and his body. He is not showing ANY signs of seeking recovery any time soon and I believe the most loving thing you could do for him (and the rest of your family) is to report him to his probation officer. It might just save his life....and yours.
There is no good that is served if he takes you down with him.