Both Scorron and Onkel Udo bring up good points.

Onkel Udo is right in that this is the fault of the 'new' environmentally-friendly switch that was made in clearcoat in the late 80's and early 90's. Dodge experienced a particularly high failure rate; high enough that the shop I worked at in high school and college could count on seeing one or two a month.

Scorron is correct in mentioning that you'll need to get rid of the clear, although I might disagree on having to get rid of the paint as well. IMHO and IIRC, the paint didn't suffer from the same issues, only the clear. Not sure if that was what Scorron was implying though, perhaps only that the easiest way to tell if you've gotten rid of all the clear is to get rid of the paint as well. That'll be more tricky for you as the Metallic Gray paint that you have will look awfully similar to your grey primer. It'd be easy on my white paint to tell when I hit grey primer, but you'll have a more difficult time knowing when to stop. And, as Scorron pointed out, you do want to stop before you get to bare metal; especially with that Alabama humidity.

If you do sand it, I would use a random-orbital (or air tool version) with a 220 or 280 grit. 180 would be okay by hand, but with a RO sander using a finer grit will buy you a little extra time before you hit that metal. Also, make sure that the pads you're using have some sort of foam backer to accommodate for the contours of the roof and hood. Otherwise, you'll get hotspots.

The other option that worked well on the hood of my dad's Dodge Dakota was to remove the bulk of the oxidation with a red scotchbrite pad or 400 grit sand paper. You have to be pretty delicate to not remove paint, so don't get too rowdy. Then wax heavily and buff by hand. You'll have to do every 6-9 months depending on the amount of sun, but it'll keep it from looking gross until it either becomes a parts car or you paint it.

Hope that helps!