Unfortunately, there probably is not a quick and snappy comeback for a man like your FIL. I have been there and done that with my inlaws when I was first married (21 years today!!!) I come home in tears after their spiteful comments many times. Finally, I told DH I was no longer going to subject myself or my children to their behavior. At the next family gathering everyone wanted to know why I was not there and he told them I would no longer be coming because of the way they all behaved.
It's funny because I have always had a very good relationship with my nieces and nephews. I'm actually helping our oldest niece move into her apartment tomorrow. When she asked for help
not one of them offered. She emailed me back to thank me and said she didn't expect anything less from her "favorite aunt".
Sometimes actions speak louder than words!
You have one of the cutest babies on YT!