I've read along with your threads in the past, but I don't seem to recall the tension with your FIL.
Is that new, or has there always been an issue? Also, what specifically happen now for him to threaten you?
My FIL threaten me (jabbed his finger in my chest and told me to get out of the house), but since my W has never had a good R with her F it was a really positive thing at the time because I stood upto him. I told him I wasn't going anywhere until my W got what she needed/wanted from the house.
Regardless obviously you don't want to attempt to stand up to him as I cannot imagine that would help, but is there anyway you can difuse the sitch a bit?
Me - 34 W - 33 M - 8 years T - 15 years D7, D5, D2 Bomb Nov 10/2010 "I'm not happy and INILWY" W Staying for the kids Mar 13/2011