I would like to see some sort of official FAQ for this game in the future.
Me, too! But, FWIW, here's an unofficial pass at your Q's:
1- Page 18: "The Hutt player may choose to try and destroy the Death Star. He may do this because the Death Star is blocking his path..."
Q. Does the Death Star keep the Hutts from fortifying or attacking if it occupies their planet? Where in the rules does it state this.
The Death Star only prevents attacks against an Imperial-controlled planet it occupies (page 14). There's no rule that the Death Star itself blocks fortification moves into or through (or prevents attacks against) Rebel or Hutt controlled planets.
Presumably the "blocking his [the Hutts] path" refers to the Death Star occupying an Imperial-controlled planet that the Hutts want to attack (since the Hutts have no Force Meter incentive to take on the Death Star).
2- Other threads state that the Death Star can pass through an asteroid field but where in the rules does this state this? A Capital Ship can't but the Death Star can? I can see leaving the area just destroyed but not passing through the area in future moves.
The rules aren't explicit, so it's anyone's guess. But Asteroid Fields only block attacks and fortification (the two methods Capital ships have of "moving"). The Death Star, however, moves by die roll in separate turn step.
3- Page 17: "You may move any additional troops and ships onto the planet as well" I'm guessing they mean from the recent attacking planet and not from other adjacent planets.
Yes. Page 8: "You can attack from any one planet..." (emphasis added) and page 9, the Changing Attacking Planets During an Invasion paragraph.
4- Can a player call off an attack and retreat back to the planet it attacked from?
Despite the "send" terminology in the Attacking rule (page 8) the attacking pieces don't actually leave the planet from which they attack (until they actually conquer the defending planet, see page 9), so no retreat is required. And a player is explicitly allowed to call off an invasion (page 9).
6- Is their a limit on the number of cards you can have in your hand?
I couldn't find one and it was one of the first things I looked for (the card limit for the Clone Wars edition wasn't mentioned in the rules, only in the Turn Sequence cards).
The 5-card limit mentioned on page 7 of the standard RISK rules explicitly notes the limit is for the standard game.