If I were you, I'd go to the police department -- and file charges of theft. He took these things without your permission. If your mailbox key is property of your housing complex or the Post Office, that is also illegal, because they do not belong to him, they belong to the issuing entity. As for your hard drive, don't be surprised to get it back non-functioning, if he even gives it back. He can be ordered to return these items to you.

If I may ask, how did you find out he'd taken these things and copied them? Did he tell you to gloat? What a jerk to do that.

Soon you will be OUT and he will have lost control. He is clinging to every little bit of control he has. Police? Revenge? If you can pull it off (legally and safely), why not? Stay safe and stay focused on the prize...your FREEDOM!