Actually, as far as I can remember, the KDZ restoration was the only thing I didn't try before. I did restore my LG G2 to factory ROM but via custom recovery backup, never through the method described on the link above!
So, anyone with touchscreen problems should try flashing back stock Jellybean firmware, then let the device upgrade to Kit Kat.
I hope this helps anyone!!!
If you need help with the KDZ flash process, please let me know and I will gladly help with anything I can!
Note: However I do feel I have lost my trust on this device that I will simply let it go soon and get something else.