But once Jack put the cork back in, the glowing magic urine started back up. So jack should have died at that moment, not climbed out and died in the forest.
like with real urine, perhaps it takes an hour or two to regain smoke-monster-turning power. jack walked out on his own fairly soon.
And how did Des get off the island at the end of the series? He wasn't on the plane and they kept telling us there was no other way to get off at that point.
ben alluded to hurley-jacob (hugob?) as being able to make his own island rules, including allowing desmond to head home to penny. maybe it happened, maybe it didn't. maybe it happened 100 years later, or maybe he hopped on smokey's boat later that day.