You need to tell him you're the CEO now and you are calling the shots. He must have forgot about your promotion.

Does your boss have a higher-up? Can you collect evidence of stuff like this happening and bring it to them to cover yourself? It sucks for your boss that he’s deteriorating this way and all, but if it’s impacting his job and/or yours you need to take care of yourself.

So start getting everything in writing with his signature. That will eliminate some of the problem

OP, the only good choice is to look for another job. But don’t quit until you get the job you need… In the meantime document everything important - Get boss to follow up with a text or email or voice message. My wife has memory problems (due to a stroke much earlier in her life) and like your boss she can be absolutely wrong about something she thinks she remembers but have no doubt of her version… By the way there are two different interpretations of your boss’s actions - Either they have memory problems they don’t acknowledge or they are a sociopath and you are being used. Either way you can’t “fix” you boss nor will you get his boss to acknowledge there is a problem because they they would have to admit having and keeping your boss in that position was a mistake.

YDI, As a professional you really need to have documents for anything that may fall into question. At least communicate through email so you have record. Probably would be useful for him as well.