The issue is not the fluid its the cylinders they need replacing, its a common issue with zeds especially ones that see track work, as the cylinders arent up to the job and as the heat builds they sieze and the pedal drops. its generally a sign that they are worn. if you dont track the car and drive sensibly you probably wont see the issue return unless the weather is really hot and your pushing it down back roads.
with regards to lighten flywheels all the ones i've seen fitted to zeds chatter, and increase cabin noise; and with cars that i've driven, the more peformance focused the clutch is the worse the car is to drive as a daily driver. but if its track work your doing its not as much an issue.
if your tracking the zed you need to improve the brakes from standard and if possible lighten the car...alot she's a heavy girl good feedback but she's not designed as a track car, she's a GT cruiser. and all that extra weight puts alot of strain on the brakes on track.