It sounds like he is using to me too, but regardless of whether he is or isnt...the way he is treating you is abusive and nasty. He brings nothing to this relationship, you do all the work financially and at home with the children. Leaving him really won't bring you more work, it will relieve you of the abusive words and attitude and give you a home filled with peace.
I think I would seek legal advice, find out your rights and plan you next move. Your children are living in an abusive home where drugs are probably being used. They deserve better, you deserve better.
Hugs