I'm bucking the trend. I don't think you got a bad truck...maybe paid a little more than I would have (depending on mileage), but still, it's a 16 year old vehicle from a state that apparently uses some chemicals and salt on their roads.
My 2000 LX has spent its life in Maine and has rust, granted it doesn't have cancer like yours in a couple of those pictures, but all in all, I don't think yours looks bad.
I guess it's a matter of perspective. I've seen and fixed much, much worse.
Anyway, If it was mine, I would fix the holes, spray some Fluid Film (or ATF) on the underside (and every nook/cranny), and run it. My only concern with your truck is that being in Texas, there may not be a whole lot of people used to doing rust repair on structural components. You can't just weld a piece of sheet metal over a frame hole and call it good. If you know how to weld, do some Googling and fix it yourself.
After a few winters, even brand new vehicles up here can look like that (and worse) unless they have been sprayed from new and all the drain holes cleaned regularly. It's a fact of life when owning a vehicle up here. We have State mandated yearly inspections, and from my (limited) observations, the #1 reason for failing is rust.....rockers, fenders, frames, etc. Craigslist for this area is full of vehicles that are great mechanically but falling apart structurally.
Good luck.