Based on what happens, when the headlights are turned on, I'd think you have a ground problem. That much current, trying to find ground, will pass through and light up everything.
But that doesn't explain the blowing fuses. Is there any chance that you pinched a wire, when you dropped the fuel tank?
When you replaced the tail lights, did you use bulbs that exceed the original wattage? Stu had a write-up, about a burned backup-lamp harness, that was a total pain to trace down.
2003 SE, 4.88's, Yukon axles, Rancho springs, JKS Disco's & MML, RE trackbars, ZJ steering, and a bunch of other stuff my wife hasn't found out about...