'97 Electrical Conundrum!

[RMCHRQB]

My '97 5.7 has 60k miles on it. Recently, I started experiencing battery drain and slow starts. The battery, a 72 month Delco (only 30 months old) would hold its charge when tested and the alternator was steady at 14 amps plus, so it looked good. However, I noticed corrosion on the positive battery cable to the alt (in the middle, under the cover). I had it replaced. At 60k I also decided to replace the dist. cap, rotor, wires and plugs (Delco platinum) and door switches (see below)...along w/new fuel filter, brake fluid, etc.

The problem is in the week since it returned from my trusted shop (not a dealer) each turnover/start takes longer. First time turnover each time but more labored. While the interior electric appears fin, in general, it is important to note that I drove the car with the dome override switch activated for about a year because the interior lights flickered upon entry to the vehicle. I had the door switches replaced as I knew they created endemic Tahoe electrical probs, so I started driving the Tahoe with the dome override de-activated. But there is still the occasional flickering. What's draining the battery and contributing to slow starts in sunny southern California? And how do I stop that interior light flickering upon entry? Much Thanks!!