You know, Bree is how old? Is she quite young? The bribes for young kids are cheap. They tend to get more expensive as they grow up. You husband and MIL will pay the price for this eventually, unfortunately it will be dumped in your lap when the problem is too big for them to handle.
I wish you would leave, I wish you would take Bree & the other two kids and just go, but I know you need to go through this journey to get to the better side of life.