Problem solved!
I returned the second faulty fuel pump, and ordered a used pump and sending unit from DC Auto. Along with those new (used) parts, a fresh fuel pump relay, and fresh fuel, the car performs. Period.
The gas I pumped out of the tank smelled old and not nearly as strong as gasoline is supposed to smell. Even after getting it on my hands, the smell largely disappeared - kind of odd. So with a dry tank, I installed the (very lightly) used pump, then the used sending unit. All locked in, I dumped in 5 gallons of fresh 93 octane (which DID smell strong). Turned the car on, nothing. Forgot to put the new pump relay in (old one was installed), so I swapped that out. Cranked, fired, booyah.
I waited about 2.5 hours and tried again. Started. On my way to work this morning (about 11 hours after the fix was completed), the car fired right up. Refilled the tank with fresh gas, then went to work. Started right back up after sitting.
I'm so, so happy to be driving my Boxster again. I sorely missed having it on the road in the last three (almost four) weeks.