My father-in-law is verbally abusive. Any advice?

You have to give more information. How old is he? Does he suffer from dementia or mental illness? Is he a substance abuser? Does he suffer from PTSD? Does he have a police record?

Many people who threaten to cut people out of their will either actually don't have one created or never get around to doing it because it costs THEM money ;-)

Tell him to go ahead and change his will. Tell him you hope he leaves it to a cat shelter.

Don’t put yourself in the line of fire, leave each time the yelling and threats begin. Let us know more about the living situation

You don't give many details but you must consider that he is decending into dementia, as verbal abuse from agitation and anxiety can be a symptom. This doesn't make the abuse acceptable, but the circumstances of what's going on does matter for anyone to give you good guidance here. Please provide more details.

Welcome, Witchcraft!
Is FIL living with you or are you in HIS home?