I'm not sure the Death Star's weaponry is even relevant to this game.
In the original Star Wars, the whole reason Darth Vader decided to take on Red Squadron is because the battle station had trouble targeted such small, fast craft. (It was primarily designed to destroy entire worlds, after all.)
Seems consistent with the "double its agility value" on Single Turbolasers. That is, the Turbolasers will have a hard time hitting anything with Agility 3+, but a pretty easy time with Agility 0-1, which tend to be large and/or more sluggish ships (e.g. YT-1300, Lambda Shuttle, other Huge ships, B-wing, Y-wing). Agility 2 is about average (e.g. 4 attack against 4 defense, which is gives a slight edge towards the attacker).
For fun, casual "Trench Run" scenarios, maybe give the Death Star turrets a range of 1-3 (and maybe a firing arc that is "trench only"?) with 3 attack and the same text as Single Turbolasers.