I'm so sorry your going through this. It feels like the addict is "cheating" and essentially they are.. but not with another person, but with drugs. He may not be ready to give in to his addiction and 30 day rehab stays (I hear) are not what we imagine they are. My AH said it was worse than jail. LOL.
You can just start to protect your money, any valuables and try not to argue in front of the innocent kids. (i'm guilty of this.) I'm here... going through heroin/opiate addiction as a wife....and it's horrible. I feel your pain.