I don't see where you have any choice but to divorce your wife and cut all ties with her family. :D
I have an ex brother in law that did the same thing to me shooting clay birds. He didn't hunt much, and rarely shot a gun at a target of any kind. The first time he shot with me, I told him not to let it bother him if he didn't do too well, after all, these things take practice to master. He broke 23 out of 25 his first time, and 24 - 25 over and over again after that. He couldn't hit a live bird to save his life, but he sure broke the clays. And no, that's not why my ex and I got divorced lol.
Just tell yourself that he had a good day, and you were off that day, and don't shoot with him again.
Bob