Oh hell -- so you installed a different fuel pump and it failed???
Is it a walboro? Those are notorious for failing rubber seals that cause a loss in pressure -- the good news is, it's usually an easy fix if you don't mind rooting around in raw fuel...
The low power numbers may or may not be reflective of impending fuel pump failure unless there is evidence that it was skewing way lean under load -- you know how it is with load holding dynos.
Once you get this sorted out, I'd just get a baseline on a dynojet which should give more easily interpretable values.
Well, either way -- good luck! Hope this gets fixed ASAP!