Do you have coaxial cabling, and how old is it? If it's more than a dozen years old or so -- or you're using twinlead ("ribbon") cable -- it's time to replace all of it with RG-6 coax. At that age, the outside run that's exposed to that hot Texas sun is probably cracked and worn out. If you get new cable, replace the $5 matching transformer used to connect the coax to the antenna -- they wear out over time, too. (You'll need it in any case if you're migrating from twinlead to coax.)
Even when working right, RS amps tend to be awfully noisy, and noise is the enemy of weak digital signals. Get a Channel Master 7777; it's among the quietest antenna pre-amps available. It comes in two parts: a module for mounting just below the antenna, and a power injector that goes into the coax cabling before the splitter, right where you have your current amp. The injector sends low-voltage DC up the coax to the pre-amp, to preclude the need for running house current outdoors.
I looked up Sherman proper (ZIP 75090) on TVFool to see whether added height would help. It won't -- higher makes WFAA's signal modestly stronger, but not enough to warrant the hassles and extra hardware involved.
That pre-amp and fairly-new coax should make a big difference in WFAA's reliability.