As I understand it a more acccurate translation would have that first line as "May your reign continue for a thousand generations..."", addressed to the Emperor.

Which I suppose is a wee bit more extreme than "Long may she reign", but essentially the same.

National anthems aren't meant to make sense. Poland's got a great one starring Napoleon. Romania's got a very stirring one featuring the Emperor Trajan. Italy has Scipio's helmet...