As to steering wander, don't forget the suspension bushings. They're usually well worn at 100k miles. When I installed the SSI steering stabilizer, it make a big difference in steering. But after a few more years, the wander was back. Finally, I fixed it by replacing the 8 bushings on the front suspension. After that, I had to re-learn, once again, how to steer the truck.
Don't depend on a static check of the bushings. Even nearly worn out, you can't put enough force on them to show they're worn. If the bushings are over 10 years old and/or have over 150k miles on them, replace them.
If you have to see the motion, strap a web cam under the truck to record the front/back motion of the front axle. You might be surprised at how much motion there is. And you might be surprised at how little movement it takes for the steering to wander.