I wouldn't do anything to help you AH find somewhere to go. He's a big boy, capable of taking care of himself. I certainly would not talk to or email your FIL. Not your place to do so IMO. Why i the world should you have to continue treating your AH like a child incapable of taking care of his own business and problems?
I might help pack since it would be in my best interestes to get it done so he can leave. It would also make it a lot easier if you end up haivng to put his stuff on the lawn.