Found the +12v at relay pin 30 (socket pin 8, directly from battery +) drops when the fuel pump stops.

I can stop/cause this by holding/moving the relay/wiring while the car is running, though can't get the voltage to stay/drop doing same while monitoring the voltage with a DVM. I've cleaned pin/socket and both look good - may be a resistive open circuit that needs a load to show up (but couldn't cause it with a 2 ohm load resistor).

Several posts say that relay solder joints go bad, and relays can be fixed by resoldering, but it will soon happen again. One said the fuel filter gets restrictive, pump works harder, draws more current/burns relay contacts, and heats joints (and recommends replacing the filter along with relay).

My pump was stuck/shorted - repeated attempts to start would have pulled a lot of current through wires/pins 7 and 8.

I want to inspect the connection at pin 8. Does anyone know how the relay socket housing comes apart? Looks like there are tabs, but I'd like to know (at least) if socket side or back cover comes off.

BTW, this won't cause the "doesn't run 1.5 seconds when key first turned" issue - that's a function of the relay. Below links a similar circuit from a 924. The 7-pin 380SL FP relay has two 555 timers, two dual flip-flops, and a smaller 2-contact relay (I started making a schematic).
924Board.org :: View topic - Fuel Pump Relay circuit diagram