Ok, so you have 12 volts on the fuses - so you are losing it between the fuse and pump. This tells us there is resistance between the fuse and the pump.
The most likely cause is bad solder on the RCM, a bad Fuel Pump Relay on the RCM or a corroded connector somewhere between the RCM and the pump itself.

The service manual shows no connectors between the RCM and the pump, I don't believe that!

If the wire itself is black, it's a sign of corrosion. The wire being black is NOT a problem itself, but if it is black, then likely where it crimps in a pin at a connector, there is a bad connection: The Black on the wire is corrosion. If you have corrosion on the wire at a crimp pin connector, you will have resistance!

I'd disconnect and pull out the RCM board. Look at the pins on the cables and the mating connections on the board - are they clean? Probalby not.

It sounds to me like the pump is probably ok - the pump is just not getting power! I am wondering if this car was allowed to get wet (flooded?) at some point.
The black conductor in the wiring is not at all normal and is a sign of corrosion.

I'd pull the RCM and look at the solder of the pins. If you can see the relays, (I think they are open-framed) see what the contacts look like. The mating surface of the contacts should be clean! If they are black, dirty, pitted, etc.... the relays should be replaced or at least cleaned.

There is another thread here where some guy found a source for new relays - new once can be soldered in rather easily.

You are getting close to the problem!