Ben,
Considering the age and the milage of this truck, most of the items repaired appear to be within reason. The rearend if not properly maintained and continously place in stressful situations will eventually fail. The 4x4 module is not an expensive item and easily replaced. Starter replacement is expected at least once during the first 100,000 miles unless mostly highway driven. Rear door handles and fog light switch probably more related to abuse than early failure. If everytime you get in the truck you lower the rear window the motor didn't fail, it has been exposed to excessive use. The stock stereo, maybe the original owner did remove it and then replaced it, but again, if every time you get in the truck you crank it all the way up, this could happen. And if the owner did remove/replace the unit, maybe during the re-installation (since he was selling the truck) he wasn't very careful. The gas tank, by your own admission was your fault. Fan clutch, typical maintence issue.
All of these parts will eventually fail and in some cases preventitive maintenance will give these parts longer life. I don't believe battery failure will cause issues with most electrical parts, however a short could, and when off-roading the truck is repeatedly placed under stress that the average truck is not.
As a student I can understand the frustration with spending several hundred dollars to repair/replace parts on a limited budget. However, a different vehicle will not be immune to many of these problems and will be just as costly. Actually, from the parts listed you have replaced, not excessive or expensive, except for the rear-end and the gas tank.
I have owned two STs, a 2005 and currently a 2009. Do I go off-road with the truck, no, and do I expect them to be cost free during the life of the vehicle, no. I do expect to repair the truck in the future as it gets older and the miles add up.
As someone earlier stated, this is just one of lifes little lessons. You will find in the future that the car needs to be fixed or the tires replaced, the house always needs some type of repair, that essentially your always going to be taking care of something and it never stops.
If you decide to purchase a new vehicle, it will be more costly in the long run. And if you decide to purchase another used vehicle, it will have it's own problems.
Good Luck with your choice but it is cheaper to keep her...