I have an odd question, and me no brain good as I finally go to bed at almost 7am after a double shift.

Dual-Turbolaser Turrets Modification 5pts. While attacking, you may exhaust this card to add one red die to your attack pool. If you do, remove one die from the attack pool.

Let's say I have DTT's and also a card that modifies die rolls such as Darth Vader, Concentrate Fire, H9 Turbolasers or Quad Turbolaser Turrets. Can I trigger modify dice effects before removing the die? My experience with weird corner cases says "probably yes," but I'm wondering if I've missed something in the timing.

No, you have to complete the entire effect before moving on to something else.

Does it work against squadrons?

Yes, it does. The card says "while attacking", not "while attacking a ship".

thanks