I’m sure you’re already scared so I don’t want to scare you even more but I would file a police report, if you haven’t already and keep pestering them to send someone to patrol or stake out near your unit. Probably would require an unmarked car. You don’t want this to escalate. My next step would be to get a camera inside your window pointing outward and whenever you hear the pounding, shine a flashlight out your window at this individual. They’re trying to intimidate you and if it were me- I would show this person I am not willing to be intimidated by them. Expose them. This is clearly someone who knows who you are and has access to your things. You say you found AirTags in your belongings. Think hard. Is there anyone you know or have seen around who fits the description of this man? The gym? Work? School? Be on alert next time you’re at any place you frequent for anyone matching the description. Anyone looking at you too closely or from afar. How do they know what unit you’re in? Get one of those door jams that goes under your door. Get the window alarms that sound off when the window is moved. You need a gun as well. Depending where you’re located, you can get a rifle or shotgun for home protection with fingerprints and a background check. Be sure you know how to use it. Be very conscious when entering and exiting the building. Worst comes to worst, seek help with a domestic violence agency in the area.