The GT PP brakes are not only larger but have a rotor that can be cooled properly. You'll need substantially better brake pads as well for track use. Carbotech/G-LOC XP10/R10 fronts and XP8/R8 rears are good options.
Yeah pads and fluid are on my list. For cooling I might get a brake cooling kit that runs through the fog lights holes. So far it's been fine though by just doing a cooldown break in between laps. For longer track sessions I'll definitely take this in consideration.
Cooling ducts will do very little with your current rotors. The venting is on the outside face so ducting can't force air to the middle of the rotor and out the vents. That's the biggest limitation of your brakes. With a Steeda or Baer 2 pc rotor, you can alleviate the issue.
Camber plates. Otherwise you've got the full package.
The springs by themselves, no. But with the roll center correction arms, yes.
Yes you need the bumpsteer kit with the arms. I'd strongly recommend them both but understand your bill is getting sizeable. They are a big part of the handling equation. I don't see anything on your list that I'd say don't bother with.
You'll be very satisfied. The car is on rails with that setup and very track competent. You'd definitely see a sizable step from the FP track kit.
Differential hardware upgrade kit. What you really need are just the steel bushings but the upgraded fasteners are gravy.
