1. There's no update to the Great Flyby Attack feat.

2. Yes, you get to attack a number of foes in the line equal to your Dex bonus irrespective of whether you have enough BAB for iteratives. By the same token, you don't get to make iterative attacks against any of those targets, even if you would get iteratives on a full attack.

I'm fond of combining Great Flyby Attack with the Surge of Fortune spell to then apply the roll of 20 to all the attacks.