LTFT are stored in MAF ranges, not RPM ranges:
There is no problem if seeing large STFT for a short periode of time. Especially coming in and out of overrun and getting on the pedal. Often it's in unusual driving conditions. As an example going downhill with a very low throttle input (like 1% throttle).
You got to look at a complete log and not extreme values on the OFT screen. If the STFT generally is low in stabile conditions everything is fine. STFT values of +/-15 or even 25 occasionally and for a very short while is normal.
100 RON is 95+ AKI (at least German 100 RON). 98 RON would be 93 and 95 RON is 91. 91 RON is 87 and I don't think sold in any civilized European country for the past 20 years.
There is a bit of variation in fuel quality between southern and northern Europe (just like in various areas of the US).