I did some research and found that there is hysteresis in the SoC vs Voltage curve. Additionally, you need to be sure you are looking at the resting voltage of the pack, not a pack that is actively charging or discharging. Finally, it is very likely that the e-Golf SoC estimation is accomplished by ...

I have seen this too. I don't exactly understand why this happens, but I agree it is related to the BMS calibration, and slight changes in temperature of the pack while the car is sitting. I don't worry about it - my battery pack works just fine.

33% less energy to preheat using heat pump, as I would expect.

Need to repeat test a few more times. Was tire pressure the same? Same wear on tires? Same wind conditions? Same car mode (normal, Eco, Eco+)? A longer drive may help, too.

I would expect more like 30%. I suspect without pre-heating cars you will see much bigger difference.

Lemon law? Or do you want to keep driving car after it (we hope) is repaired?

I mostly use car scanner and have learned through playing with the software.

It works fine for me. I have always shipped tires to my independent repair shop. I never needed to try to get warranty service on a tire because they have worn out before I had any issues.

Have you pressed the correct button to the left of the charge plug socket? Which button is lit up when you charge?

Motor torque ripple?

One more comment:

I think a good rule of thumb is to have BEV with a range at least ~1.5 times your daily commute for convenience and unexpected needs.