That's centanly one interpitation. However, the information is being provided by Spock during the mind meld. Calling him "Last of the Romulan Empire" wpuld be like referring to Checkov as "Czar of all the Russias". He may have called himself that but it's not relavent to the point Spock was making.
Yes, it is. Because Spock
wasn't calling him that -- Spock was reporting what Nero called himself
. And that is relevant to establishing Nero's state of mind, his motivations. And that is part of what Spock was conveying in the meld -- who Nero was, why he was doing these things.
Seeing as the Hobus Star was a fair distance away from Romulus and still managed to utterly destroy the planet it stands to reason that the otherRomulan colonies, particulary those older and more established ones, would be destroyed as well. How many Romulan colonies have been mentioned before anyway? Perhaps the Romulans have captive planets but very few that they've colonized themselves.
Let's keep in mind that canonically, the star has no name. "Hobus" comes from Countdown
, which isn't entirely consistent with the movie, since it shows Spock and Nero establishing a relationship before the supernova, while Spock's lines in the meld -- "He called himself Nero" -- suggest that they'd never met before. Neither do we have any canonical information on the star's position relative to Romulus.
That said, the movie did seem to indicate that it wasn't Romulus's own star that went supernova, because if it had been, there would've been no delay to allow Spock to undertake the red matter plan. Of course, that would raise the question of how the radiation got to Romulus in days or weeks instead of years. Really, the whole sequence of events as presented in the movie is scientifically nonsensical, and Countdown
's version adds even more impossibilities and absurdities to the account. (For instance, asserting that Hobus was one of the oldest stars in the galaxy. Stars that old don't go supernova. It's something that only happens to very large, very short-lived stars.) So I'd hesitate to accept anything we've been told about the supernova, canonically or otherwise, at face value. It happened, but the rest is subject to interpretation.