Wow, that last bit is super-passive-aggressive. Still, this is probably my fave part:

"I left a very angry (but not threatening) message on his voicemail. I simply explained to him that he was very lucky to be 3000 miles away and that if he ever contacted my wife again, there would be a problem."

I'll finish with this...if you hate your mother-in-law and she wants you to die in a grease fire anyway, why do you care that she used to support a person you also hate and shouldn't care about? I think you're stressin and you shouldn't. Live your own life.