You have children, if you leave him he is responsible to support them. Have you been to an attorney? At least to see what your rights are.
One of my bounderys when I was with ex-abf was NO DRUGS in the house, he never crossed that one. He knew I would toss him out faster than he could say Goodbye. Just wasn't going to happen.
Your children are your priorty, end of conversation...you can lose them by allowing drugs in your home. This should not be an option.
Do what's right for you and your children.