Suppose you have a ship with Vader crew and Gunner on board. You have 2 hull left.

You make your first attack and miss. You trigger Vader, destroying the last two hull you had.

Do you still get to make the second attack with Gunner or are you destroyed then and there?

You get the second attack even if Vader destroys you after the first. It's in the FAQ p 12.

Nevermind....

Are you then able to trigger Vader a second time?

How could you, seeing as you'd have 0 Hull left?

How could you, seeing as you'd have 0 Hull left?

But Hull NEVER decreases during a game. Ships only acquire more damage.

Sadly the FAQ answers that one too

A ship equipped with Darth Vader can use this ability if
it has at least 1 hull remaining.