Mike, thank you for the reply. We went around tonight checking voltages and trying to activate the fuel pump with a secondary battery to narrow down the trouble site in the fuel pump wiring. I forgot about this orange wire near the battery and didn't test that.
However, we were able to start the fuel pump at the connector nearest the fuel tank. Then it couldn't be started from the fuses, and we continued to narrow it down like that until we found a bundle of wires in the trunk immediately behind the back seats. We fiddled around with that, looking for a bad wire. One of them, a black ground wire, was disconnected from the chassis. However, it had rusted and looked like it had been disconnected for quite a while and therefore could not have been the cause of my no-start problem, which began three days ago.
We stripped the grey wire of the bundle (according to the Haynes repair manual circuit diagram, this was the fuel pump wire) and tested it to see if it was getting any volts when we turned on the ignition ... WELL ... we heard the fuel pump start up and pressurize the system!!! We were able to start the car at this point!
It seems that something in this bundle of wires was not quite making good contact somewhere, and our fiddling around with it completed the circuit. We gorilla taped down the bundle of wires to the body of the car underneath the carpet of the trunk instead of having them float around ***** nilly, and the loose ground wire was repaired. Car still started after this.
I will update if I still have the starting problem (the thing that happens 20-45 min after parking, which I began this thread with), but for now ... a beer