Neither of these are clarified in the card almanac at the end of the rules:
Water Bug - Am I right in assuming that this still doesn't score reruns in end game scoring? Just so I know if I lost by 5 or 10 in my latest game (and more usefully for information going forward. Though I do wonder if I managed to lose with 293 or 298 to 303)
Correct, it doesn't, unless you have Daytime Soaps, which lets you score a Rerun in final scoring.
Eternal Zest - It has no preferred timeslot. For ads that flip if they're not attached to shows in their preferred timeslot, does Eternal Zest flip or not? (This didn't come up, since I was able to secure a promo before taking it, but it could have come up this game)
They are not considered to be in a preferred time slot because the show has no preferred time slot.