I suffered years of horrible treatment from my father in law. In public he was completely charming to me, to an uncomfortable level, kissing me, constantly having his arm around me. Behind closed doors it was a whole different story. His comments were cutting. I found I was constantly pandering to his approval. My husband would ignore his behaviour which at times caused friction in our marriage. He said to me "don't ever get on the wrong side of my father, he will drag you down to his level, just ignore". However, my in laws marriage ended and so did the marriage of the golden child (my husbands older brother). Suddenly my in laws treatment towards us became worse. It was like they couldn't stand that my husband and I had a lovely relationship. They started to sabotage our marriage. Then they involved our kids. One time my father in law sent our 10 years old son a birthday card in the male. Inside the card he wrote "sorry this card is late, poppy has been busy with secret mens business. You will one day learn about this. Women also have secrets, even your mum". I ignored this on the advise of my husband. However, it continued. Eventually, I reached breaking point and told him that he was no longer welcome in my life. His reply was "You need to respect your elders". That was over a year ago and we have had no contact since. I look back and the events preceding my final decision, and can't believe how sick and terrible I felt during that time. It was a pretty dark period in my life. I was told that my father in law has NPD. I read about this disorder and it was a huge moment in my life. It was as if for years I had been looking at a distorted picture that suddenly became clear and I could - for the first time - see the whole horrible scene.
I'm so sorry you have suffered through all of this! I'm glad that you are no longer in contact. You tried the best you could to make things work. Many times we do try to keep the peace for as long as we can. NPD is awful and is extremely hard to deal with. I'm very glad you are no contact. It is also best for your son as well.