That's terrible.
Your father-in-law make some kind of despicable public spectacle of himself at a party that you WERE NO LONGER PRESENT AT,is consequently told to step down, and somehow this is YOUR fault?
...and your wife sides AGAINST you with her father?
You've just uncovered a genetic disposition to low morals that seems to run through your wife's family
I hope you have no children to further complicate things.
This will be HELL to get through, but once it is done your life will be so much better. You have my best wishes. Please keep in touch.