2002 C5 Chevy Corvette Z06, T56 Manual trans, 45k miles. Bought the car about a month ago, 2 owners good records. 

Ive been going about changing and refreshing all the fluids in the car since some records were spotty. Changed the trans fluid (T56 calls for Dexron 3) to Valvoline Dex/Merc about 500-600 miles a week or two ago. After the fluid change I noticed more gear notchyness, more syncro/gear mesh noise, more 1st and reverse syncro lockouts requiring double clutching or going into 2nd then into desired gear. All signs the trans wasnt happy with the fluid so I just swapped it again to Redline D4 ATF and so far its better. 

I didnt have the car fully level at the time of doing the first trans fluid swap, so its possible I underfilled it by maybe 0.3 quarts at most.

Heres the question: I noticed on draining this only 2 week old only 500-600 mile of service as a daily and spirited driving car yielded this much shiny glitter, versus the fluid I pulled out 2 weeks before that may have been years old was a sort of grey amber but no noticeably glitteries.

How badly did this fluid damage my trans would you guys wager? How much glitteryness is for sure damage versus normal for these transmissions? I ran a magnetic over it fairly well and only found at most the tinniest bits of grit that I could faintly feel that it picked up when going around the bottom of the pan. 

Just looking for feedback, any is appreciated. I plan to give it another couple weeks of driving with this fluid assuming it improves on all fronts, and may vaccuum out a sample to see how its looking then. 

Scale of 1-10 how bad is this ATF for only 500 miles?