Air cleaner would be a good start, disconnect the cleaner from the intake just for a test.
Easy enough to test the lift pump, could cause the hard start but not the black smoke.
Sounds like it could be leaking injectors. The leaking seals that were replaced... Did that involve opening the pump and lines? Any possibility something got in the pump or lines and is now in the injectors? Might take them off and get them tested and set.
And if the injectors are dumping fuel, the oil could be contaminated, explaining the white smoke from the breather.