The rust is even worse than I thought, I gutted my trunk to work on a new amplifier mounting location and saw that the driver's side wheel well has rust all over the seams as well. It might be possible to grind this rust down and repaint, but I'm really worried that the whole wheel well might be bad in which case I would have to do what repairs I could and get rid of the car sometime in the future
The rust is all because of a really crappy repair job that some shop did on my car before I bought (carfax report shows the car had "major damage" on the rear quarter panel). I can see traces of bondo and paint overspray. A good repair job would have prevented this, now I'm the one that gets screwed.
Lesson learned- don't buy a car without running a carfax. Mine showed up clean for all the major problems, but had I known the car was in an accident I would have looked over the damaged area extensively... and probably not bought the car.