Hi luv...I know it is so difficult to wrap one's head around, but there is not anything your husband's family can do to really affect any changes in his life. At best they can provide temporary fixes to long-term problems. Real change will only happen when HE decides he needs to change, not because those around him try to manage him. Real change will only happen when he is allowed to face the consequences of his choices unhindered.
Sometimes when we try to help our A's, we are really just getting in their way. And I know I always found it easier to blame my XABF's drinking on the bartenders who served him, his friends who videotaped him drunk, and his parents who made him feel bad about himself...but none of those people poured the booze down his throat, stole money from me to buy beer or pot, contacted other girls online while he was drunk, or passed out in my Christmas tree. At some point I had to accept that no one could "help" him change until he was ready and willing to do it himself.
Once I accepted this, my life and my decisions became much more easier to deal with. I wish you strength and courage.