But why couldn't Data then fire another (several?) round of torpedoes, thereby destroying the Destroyer (and Vader; at least distracting him), instead of just running off with the plans?

Alternately, he could have flown the Enterprise away, out of Vader's range. Surely it could have broken those wimpy tractor beams.

Uh... whoops. Guess I took that bait hook, line, and sinker...

I am the Doctor, and THIS... is my SPOON!