A: File a complaint with the Maryland Insurance Administration. If you go through their online complaint process, you get more information. (They probably won't actually do anything. But they'll get you straight answers.)
A: It sounds like you were an excluded operator on your family's policy. That means your family's policy on the car will not cover you. If you had another policy, (i.e. you also own a car and that car has insurance) then it may under some circumstances provide coverage. But that sounds unlikely.
It's possible that he's suing you because he needs to as part of an uninsured motorist claim. Uninsured motorist coverage protects him against being hurt by an uninsured driver. If his carrier is denying him coverage (perhaps because they think both of you were partially at fault in the accident), he may have to sue you as part of suing them.
It's also possible that he resolved everything with his insurer, and that you're being sued by his insurer. Auto policies allow that insurer to sue you to recoup any damages that (1) you caused and (2) they paid for. To win, they need to show you're at-fault for the accident, but apparently they think so.