There's no jackpot. If you keep the ball alive through the entire tour, you'll go back to normal play, but can't collect additional mansion rooms until the ball drains.

Mine came with the original L-1 rom, and when I switched to a Gold rom I noticed a number of improvements in kickout timing. If later versions of the standard rom incorporated those changes, they would probably be a better choice.

The other rule change I noticed which wasn't mentioned, is that starting multiball from the vault starts the jackpot value at 15M instead of 10M, and in my original rom it's 10M whether you start from the chair or vault.

The 3- and 4-way combos for 5M and 10M are in the gold roms as well.

Yes, you can use any normal wedge-base LED.

If a full plunge only reaches the skill shot, the most likely cause is that the shooter rod is not aligned with the center of the ball. If you're just saying that it's an easy skill shot, well yes that's true.

Yes, iirc there is a switch right as the ball enters the subway leading to the swamp.