So I did some reading in my free time to better understand the nature of black holes. I've concluded that if Bingo's hypothesis is right and the red matter compresses existing matter, then indeed it would not increase the gravity in the area and would not affect Delta Vega. It's a theory that could rectify my dissatisfaction with that aspect in my mind. However, I still have some problems:
What force is it that sucks up the planet or the supernova? I always assumed this was the gravity of the black hole, but if it is compressing existing matter, what is it that pulls it in?
Once it has compressed the matter, how would its gravity reach out and grasp anything outside the reach of the red matter's reach? For instance, if a black hole were created to suck up the supernova, it could not conceivably hope to use the contents of the explosion to create the black hole; it's obviously hoping that the gravity of the black hole will consume the supernova, but if it's not contributing any additional matter, its pull should not be any stronger and thus should be unable to stop the supernova.
The line in the film suggests (though not definitively, so the other interpretation is viable) that the black hole was created and then was consuming Vulcan, not that it used Vulcan to create a black hole.
A different point: even a supernova much less than 100 lightyears would not be enough to blow up Romulus, though it could certainly destroy most are all life by its radiation.
http://en.wikipedia.org/wiki/Near-Earth_supernova
Regardless of any of my misunderstandings in relativistic physics, clearly a number of my points stand as scientifically untenable.
005, I agree, I don't think everything travels through time. I don't think that having it be supernova-powered would make a difference in the real universe, but whatever the explanation in Trek, I believe it was more the exception than the rule.
And I'm glad to hear that about the comics, because even the battle between the Kelvin and the Narada seems to involve very different weaponry than demonstrated in TOS. Heck, the Kelvin's design even looks very different from any other Starfleet vessel of the time, and it seems that the alternate Enterprise is a continuation of this design. So I can believe that it was already an alternate universe, and quite honestly I'd prefer in some ways to think of it that way.