Looking forward for the results. Did they cover the shipping costs?
On my end, while messing with the refresh rate (trying your method), I saw something curious: the detected sync polarity was +/- (in the CRU), however the documented polarity (in the pdf from LG) for this resolution is +/+, so I did a reset of my custom resolutions and changed the default ones to +/+. So far this seems to work or maybe the tears have become way less frequent, but I haven't seen one in a while and before that it was like every hour at least.
I've also found out how to calibrate it to below 80cd/m² with TrueColorFinder, but on my display I can only go down to 66 for some reason (0 brightness via OSD gives ~50).