charlesrshell, as we said, you have done an excellent job designing and building this distribution panel. However, I am having a hard time visualizing all your hardware and wiring just by looking at your picture. Do you have an actual wiring diagram of all the hardware you have there?
As far as the attenuator in this setup
View attachment 72254. The idea is if you
still have (from whatever source) UHF interference, adding the attenuator will attenuates the interfering signal to a level which will not interfere with the UHF remote signal any more.
You have to understand that the attenuator is a passive device and it cannot distinguish between the interfering signals and the desired signal from the remote. That is why you could
not add such an attenuator on a standard setup where the antenna is behind the receiver. However, since the UHF remote will be located in the same vicinity (TV2) as the antenna (line of sight), the signal received by the antenna and sent to the receiver could tolerate a much weaker (attenuated) signal and still be strong enough to function properly compare to the standard setup where the antenna is behind the receiver and the UHF signal from the remote has to penetrate through several walls/floors and other obstructions like electrical wiring and metal pipes. Unfortunately, its is not a simple explanation but that is really how it works.