Personally I wouldn’t wait to get to that point. Had I made it clear early on that “used to be okay” jokes or comments were not, in fact, okay, I probably would have saved myself a lot of heartache.

Confronting loved ones over unacceptable behavior is a necessary skill that takes practice to develop, and I would have been better served if I had done so from the start with my in-laws.

Perhaps I wouldn’t repeat OP verbatim, but there are a lot of ways to get the basic point across.