You're probably right, with one significant "maybe not": the Bill of Rights originally applied only to the Federal Government, not to the states. A series of court decisions from the 1920s through the 1960s applied most, but not all, of the BOR to the states (freedom of speech, unreasonable search and seizure, double jeopardy, jury trial in criminal cases, all apply to the states; requirement of a grand jury in criminal cases and a right to trial by jury in civil cases don't). The Supreme Court could still hold that the RKBA is binding on Congress but not on the states.
If you buy that, then all federal gun control laws are unConstitutional.
Yes, up until the 14th Amendment made the bill of rights a part of every states Constitution. (i think it's the 14th, maybe the 12th? I dunno, but I know it's in there!)