extended cranking after a long period of sitting is def fuel related. hard start, then pressure builds.

the ls6 cam will show slight misfires while scanning, but if two are standing out then it's an issue.
determine if the misfire is no/little spark or no fuel. or could be compression related.
valve spring, compression test, wiring, injectors, plug, coil, wire, etc need to be checked.

perform a vac leak using a smoke machine also.

with all those codes, o2's especially, the pcm will never go into closed loop so ltrims/strims will not register.
using the scanner, what does the o2 data look like? what are they doing? mv, graph, wave, etc.