If the core set is in Australia FLGS for sale next week, I will eat one of my Tie Advanceds

Please post the video.

Where are you guys getting the rules reference link from? I'm seeing the link to the rules on that page, but not the reference.

1. A ship can attack squadrons, any in their field of fire. So if 3 squads are in your firing arc, you can spend one of your two attacks to fire on ALL three squadrons?

Yes - a single attack can target all squadrons within medium and short range in an arc.

2. Can there be more than one commander in a fleet, so long as only one is declared aboard a flagship of which there can only be one?

No - a fleet may have only one commander (from expanded rules reference).

3. You can only spend one defense token of each type per attack -- but can spend multiple tokens of the same type per round, assuming you have them availible?

Yes - if you had two redirect tokens you could use one defending against the first attack and one defending against the second attack that round.

4. A defense token spent after being flipped goes from being exhausted to discarded -- meaning a single token could potentially be used twice in a round but then lost? Depending on question 3 above, can it be used twice in a single attack or just in a single round, before being lost?

Once per attack, but potentially twice per round. i.e in the case of Brace - a ship attacks you with 6 hits, you can flip brace from green to orange to make it 3, but you cannot use it again to then go down to 2 (1/2 of 3 rounded up). However, if their second attack shot you and did 4 damage, you could then discard your now orange brace token to reduce that to 2 damage. But that would be your token gone for the game.

Answers added for you

Splendid. Thank you very much!