You're in a pickle. If your wife sided with you, you'd stand a chance. But with the present situation you've got a big problem. Try to do something, anything with your father-in-law. Play cards, take a walk, watch a baseball game on TV, or something that he likes. Anything to try to make his miserable life just a little tiny bit better. You'll make a friend in an unlikely spot and who knows ... maybe God will take mercy on you for showing kindness to the poor guy who took the brunt of the crap so far.
My M-I-L was a total B word. We warned her. She didn't listen of course so we cut her off for 10 years. That was 5 years ago. Now that she is completely through menopause she's mellowed out and considers my wife her best friend.
Good luck and write back if you have more questions.
Surf