I share alot of the same symptoms as your father. Irritable, thinking everyone has an angle (which causes fights), won't go to the grocery store for the basics, can't sleep, have nightmares, overwhelmingly angry.

These aren't characteristics that I had until I went through a bit of trauma. I have been diagnosed with PTSD with psychotic features and bipolarism.

Naturally I can't say what he has, but I'd say those are certainly signs that something isn't right.

Good luck!