My father has been imagining things since his stroke. First he imagined that my sister tried to run him over with her car and went to the police but the detective did not press charges because he had no witnesses or evidence (because it never happened). Now he has called all of his credit cards saying I stole and used them and he may have even gone to the police saying this. Even though I never stole anything from him I am concerned because I helped him with his bills, helped him make purchases and many times made payments on his accounts using my bank account. He lived with me for two years until recently he moved into a senior apartment because he was alone too much because of my working hours.
Keep another record of your dad's financial accusations, that he accused you of stealing his credit cards.
Keep a record of anything you pay for him such as a bill or purchases. Keep the receipts. And in this same record keep notes on if you paid a bill on his behalf. Online/by phone bills always give a confirmation #. Record those numbers.
There may not be much you can do about his paranoia but you can try to cover yourself as much as possible.
Has your dad's Dr. been informed of this behavior?