I always assumed it was Rey who triggers R2’s wake.
Here’s another plothole for episode 4: if Leia knew they had a tracking device on the Millenium Falcon, why did they go straight to the rebel base? Why not go to some moon, rendez vous with some rebels and use the MF as a lure later on.
According to the people who made the movie, you’re wrong. But I don’t blame you for assuming that, because the movie didn’t make their intentions clear.
That’s the filmmakers explanation and you can take it or leave it. The official, in-universe explanation is still open to a different explanation.
Since the explanation about R2 getting the map from the Death Star computer is their intent, I doubt they’re going to clarify it any further. But if they do, then great, problem solved. As I’ve said again and again, if they leave it as it is, without any further explanation in later films, I think it is a problem. If they go into it in further detail later on, I think it’s fine.
Regarding the details of the Republic and First Order, you’re right, at least the movie has clues so you can kind of piece it together. There’s literally nothing in the movie that suggests that R2 got the map from the Death Star, or that he “heard BB-8 in his coma” and slowly woke up as a result.