That fluid didn't look terrible at all. Lubegard will definitely not hurt anything and it's cheap enough. The dry fill capacity of a C6 is about 12 to 13 quarts so a full bottle is fine.
Hopefully they don't completely get rid of TES295 formulation, I just looked up Transynd 668 and it looks kind of disappointing, no PAO on the SDS and the Brookfield at -40 is just listed as less than 13000cP whereas the old Transynd 295 listed it as 8500cP
Might be interesting to put a 't' in the vacuum line down at the modulator valve and snake a hose up to a gauge in the cab just to see what the vacuum levels look like driving down the road.
Not necessarily, even the marketing documentation mentions helping eliminate torque converter shudder and clutch chatter, SAAB had approved it for eliminating noise on the 2-3 upshift on 9000s with the ZF 4HP18 transmission.Lubeguard Red is a protectant and meant for preventive measures.. It won't solve any problems.