Regarding old/low milage versus new/high milage, if you're putting only 5k a year on the vehicle, I would steer towards new/higher milage. If you were putting a lot more miles on, I would say steer towards old, low milage. Maybe this would be different in the salt-free south, but there are "miles related repairs" (engine failures; brakes, etc) and "age related repairs" (rusted brake lines, cracked hoses, etc). You're driving little enough that you won't incur miles related repairs that fast, and if your vehicle is new enough to avoid the age related repairs, you should be better off on average.
Plus, you should try to get vehicle with electronic stability control to reduce your odds of an accident/dying especially if you're towing, and in your price range, that's only going to be available on newer high milage vehicles.
If the space works for you, a Pontiac Vibe would be the longest lasting/cheapest to own $5500 domestic wagon/SUV you could find. Nominally it would be similar to the PT (dodge neon platform versus toyota corolla platform) but you might find the space works for you; it has reasonable room behind the back seat. And its available in awd with 1000 lb towing. It lacks the stability control, but is lower and less prone to roll.
Assuming that's too small, all of the domestic SUV's have pretty similar reliabilities. In your shoes, I would probably just look around for a babied, higher milage vehicle with ESC. Probably an 05+ Explorer or an 06+ Trailblazer from a private party seller.