Alright, I worked it out and have a clean crisp default Glo HD. Thank you so much!
In anyone bumps into this thread in the future, this is what I've done:
Now, to restore the backup .img you've sent to me, I couldn't download the required "Flash Drive Read/Write" software from vconsole.com at this guide;
https://www.mobileread.com/forums/sh...d.php?t=209122
because their pages didn't provide anything, probably changed over time.
Instead, by doing a little search on the net, I've found this small software someone independently made, someone who also seem to have love and fight for animals so it's worth giving his website a click when someone needs it:
http://www.roadkil.net/program.php/P12/Disk%20Image
This software successfully restored the image to the SD card in a couple of clicks.
And then, I have followed the instructions at the post below, because
I don't want to sync or update the firmware at all;
https://www.mobileread.com/forums/sh...1664&p=3011981
Zeroed the USER column in sqlite db of kobo, and it launched without in need of sync.
It's working beautifully now.