Not exactly. Until means not before, but right then, in this case. So we didn't get home except at the point of midnight. Not before midnight, but we did get home at midnight. You could say "we got home at midnight," and it would have the same meaning, but without the idea that you got home later than hoped or expected.

Yes, here the word 'until' is used to replace 'before'. In other words, it implies- we got home after midnight.