I’m so sorry to hear that. My dad is very similar to yours too. He is a narc & a nasty tempermental bully too.

Try avoiding talking or seeing your dad. If you have to if you want to, then communicate with him over email & text to where you can’t see or hear him yell at you.

Grey rock him. Bullies love getting reactions from people, so put on your best poker face.

The dementia will probably make his temper worse. Use deep breathing excercises & take stress gummies like a Ashwangada that you can find at every drugstore.

Talk to a therapist about this too.