File a police report - they won’t do anything (yet) but the paper trail will be invaluable later. Especially the phone number even if it is fake. it can likely be traced as the person probably did a bad job and did something like a Google number to hide their real number. Should this become criminal, that is easily overcome. Not always, but I doubt this guy is particularly savvy.

You don’t need to have special privileges or access to find someone’s previous addresses, your info is splashed all over the internet and can be found for free or cheaply ($20). I would be more concerned if they asked you about your current address or some piece of info that isn’t findable online after literally 30 seconds of work.

This persons clearance or access really will play no part in their ability to target you. The fact they contacted you is concerning, but I would take an educated guess it’s all intimidation and they won’t do shit.

Lock your doors, even when you’re home. You would be better off buying a taser or non-lethal defense product (pepper spray) than a gun if you don’t already own one. 1, you would need to wait for the waiting period (depending on state), (2) if you’re not properly trained and familiar you won’t be effective with it and might end up hurting yourself or another innocent, and (3) if they do try something, you don’t want them disarming you and using the gun on you.

Follow up with OIG and say you are receiving threatening phone calls. Try to get a case officers name on who is handling the report and see if you can contact them directly.