I'm another "change the CPS" guy..... (I too don't like throwing parts at problems, but it is a strong candidate, doesn't cost that much, and the worst outcome is you'll have a fresh CPS installed, and a still working one as a spare).
7.3 electrical - aside from Glow Plug Relay (obviously not your problem), the main common problems on the 7.3 usually are the fuel bowl heater, and the injector harness itself.
The fuel bowl heater (under the filter) can melt, and short out to the housing - often takes out a fuse, but haven't seen enough to say that it always will.
Injector harness can get intermittent over a long period of time. Buddy of mine just did his, initially because of glow plug problems. Dorman has a great harness replacement kit, that includes the (truck) harness side connectors too. (Glow plugs and injector wiring pass through the same connector).
How many miles on yours ? The factory harness is decent, but high hours of diesel vibration can take its toll.
Rgds, D.