I find it difficult to picture any sort of damage that could be caused by high pressure which does not allow as much fuel through the injector. I also know of more than one person who has blocked the return line in their D-jet system without permanent damage.
You can bench test the injectors relatively easily. Presumably they are accessible? It is probably just one M6 (10mm wrench) nut that holds them in; the electrical and fuel connections should stay connected to the injector pretty easily. Stick the injectors into some glass jars and watch them while someone cranks the starter. You can check that the fuel quantity roughly matches, and watch for the spray pattern that way.
Disable the spark while you're doing this, just for safety.
Odd thought: Is your fuel pressure gauge correct? I had one that read significantly high, and when I set the pressure according to it my car would just barely run. Fortunately my mechanic double-checked it with his own gauge and found the problem.
Have you read through the Brad Anders D-jet website yet?
Brad's '70 914 2.0L
--DD