Gosh, MM22, you’ve got a real pickle on your plate.
Look at the bright side; your father in law has (had?) to live with MIL’s kvetchy-ness 24/7!
Bottom line is, if you’re not on her payroll, you owe her zip. Not to say, be nasty to her, but you don’t need to answer / be accountable to her either,
And consider having the friend she hates so much move in with you!