Residual fuel pressure is only an issue when starting a hot car. Fuel pressure is built instantly and is maintaining it is not an issue over night.
"My manual says that this means there is a problem w/ the fuel injection system or emission control system.
I don't see how that could be contributing to the problem, "
Before you can hope to fix this car you need a lot of training. The above quote indicates you have a lot to learn; actually it indicates you know almost nothing. Sorry to be blunt!
All the information required to address your problem is described in the archives.
Bosch Master, ASE Master, L1
33 years MB technician