An easy test for a fuel problem is to spray some starter fluid or carb cleaner into one of the vacuum ports on the throttle body. If the engine fires for a few seconds, then dies, you have a fuel delivery problem.

You say you have 12V at the injectors. Have you checked for ground at the injectors?

The injectors have a constant 12V positive through the RSR. They fire on an ECU provided timed ground. To test for ground from the ECU, reverse the test - using a test light, tap a known good 12V source (battery works) with the positive lead, tap the ground side of an injector plug with the negative lead, and have someone crank the engine. The test light should flicker. If no light, then suspect the ECU, especially if you have the pink label 561.

I may have mentioned this before, but several years ago, my daughter's 89 740 - Bosch - had all of the same symptoms - good spark, fuel at the rail, wet plugs, no fire. It turned out to be both fuel pumps. The in-tank had failed, and the main went south doing double duty. You only have one pump - in the tank - but if everything else checks out, the only thing left is the pump.