Father is 83, has 90-year-old wife. Friends and family members are cutting off relationships with them left and right because of the intimidation. We wonder if this change in personality in the past several years (actually, a worsening of tendencies long present but also basically submerged) is due to aging, medicines, an illness, or what exactly. Father is not open to any criticism, thinks he is always right, and no one can possibly suggest to him that something might be seriously wrong with him. I cut myself off from him two weeks ago. One of my brothers did so today. Long-time friends of two decades did so a few months ago. What can we do or should we do?
I'm not certain there is much you can do, especially since he has come to distrust everyone. You perhaps could write out your concerns and send them to his doctor to alert him to the changes you have seen in him.
I would keep in touch with your step mother if possible. At 83 with the behavior you describe, something will happen. Be ready.