I finally read your whole book of a story, and your exfather inlaw reminds me a lot of my ex's father and mother. They were originators of grand parents rights in the 80's. And the general innuendo would be to sue almost anyone.
The only thing I can say to you is that this is also the parents of your wife. She had to deal with them growing up and I am sure that was not easy. What was she saying or doing during all these trials and escapades with her father and step son? Did she make her wishes known to you? What was her childhood like?
I can say with much certainty that DB'ing works. If you are looking for a magic button, or a quick fix I will also guarantee that you will not find it.
