you are taking these issues really serious, so I will try my best to give you some useful comments.
First of all I’m not convinced from your measurement approach, I don’t believe an accuracy of 0.1 to 0.2 mm in this configuration.
However, the quality of the prints is the main topic. Let us assume that we have no mechanical issues, then we must discuss about the fine tuning of your print settings.
On your left picture you can see a lot of little holes. That is one effect which is quite unusual for me. Here it seems that material is missing. From my experience up to now this is in indicator of slipping in the extruder (feed rate too high or extrusion speed too high). This will cause local variations in the print width, which can be interpreted as backslash. For such extreme holes I would assume a very hot extrusion temperature.
The right picture them confirms this impression. When the printhead is moving from one part to another, the pressure in the nozzle is removed but the filament is heated up above your setting. this makes it very liquid, and after the restart of the extrusion much more material will be printed for a short time. This can cause this impression of backslash once again.
So my first impression is, that the printouts are not that bad, but some optimization on feed rate and/or extrusion speed as well as the temperature can improve. Especially the fan control can have a significant impact on the quality of the prints, because it will significantly disturb the thermal equilibrium at the hotend if it is changed during printout. The temperature control algorithm in the firmware is not capable to handle this disturbance properly without large variations of the hotend temperature.
Since I was long time in doubt about the proper results on my printer too, I summarized my results and findings here: http://ddd.k8400.hoehnemann.net/. I invite you to share my findings and give some feedback based on your conclusions.