Hi Sadie, I'm sorry your husband has relapsed after such a promising recovery. In view of you having children in the house, have you taken steps to make sure he isn't in charge of them while high? Do you have any behaviour you just won't put up with, such as obvious intoxication, from your AH? You may want to consider not having him in the house while using.
I agree with the other posters that you will need to quarantine as much of your income from AH, including what you can get from his salary, because he should be supporting you and children, not spending it all on his DOC, and counting on you doing it all. Will he agree with diverting some of his wages into an account for the purpose which he can't access?
It's worth keeping a diary and any relevant documents if you think this will end in you needing legal advice. Showing him the consequences of his actions may be the only way to get him to reconsider.