Sounds like you handled it amazingly. I'm sure SIL felt uncomfortable being the one to serve you the papers so you reaction and your being dignified and classy must have been a huge relief for her.
If you can stick it out for the night and be the great guy that you are I say hang out.. but if you are starting to feel angry or aggressive or agitated I think a walk or a drive would be better than a backslide.
Nice to meet a fellow Canadian.
I hope tomorrow is a better day for you. "Happy (early) Canada Day"
