My elderly father terrorized me

I always knew my mother was abusive, but I see now there's a part of me that wanted dad to be safe, but he's not safe for me either.
He has lived with my husband and me for just over three years. I truly believed he would be with me until he died. He's 83 now.
Ever since he's been with us, he always talks about buying a car. I drove him anywhere he needed to go until recently. It was really stressing me out because he always comes up with someplace else to go. Sometimes we are out shopping for 4 or 5 hours. It had gotten too far out of hand, so he began using a local car service for seniors. I thought the problem was solved.
Nope.
This past week, dad comes home with a car, if you could call it that. It was pretty banged up. We couldn't figure out how he managed it. He only gets social security. Turns out one of the car service drivers sold it to him and was going to let him make payments.
So knowing full well that my husband and I made it very clear to him that the reason we wouldn't let him drive is because we worry about his safety as well as others on the road, he still chose to go around us.
I was furious, but I knew I couldn't deal with him without losing it so my husband agreed to talk to him. I thought it was over, at least for the time being.
Shortly after my husband left for work that afternoon, Dad calls my phone. I hung it up because I was too unstable emotionally to deal with him. Then he stood at the bottom of the stairs shouting my name. I thought surely he'd realize that I didn't want to talk to him. The next thing I knew he had managed to get up the stairs (very bad knees) and pounded on my bedroom door. I lost it completely. I screamed at him several times to go away. He started talking, most of which I didn't hear because I was now screaming at him to shut up - at least a dozen times but he just kept coming at me.
I shook from head to toe, and I can't stand to look at him. It makes my heart rate go up as well as my anxiety. My throat hurt like hell the next day.
I don't come out of my room if my husband isn't there.