Go to your boundaries that you have established and are continuing to establish. Yackers are going to yack. Whether you tell them or not. If you want to reduce your chances of them gossiping, I would reduce or cut off contact with your IL's friends and associates.
Other than that, I would just work on letting it bounce off you.
Your IL sound sneaky and backstabbish. How would you protect yourself from getting hurt by those kinds of people?
