Hi Mykola,
I can only repeat what Neels has been stating: It's great of you to reach out and share your experience. I myself haven't played with such more modern nano3G devices/firmware. However, it's good to see you looking into this and sharing the results.
It would be great if you could add your results, config files, etc. to the osmocom wiki and make the information available to the wider community. Please register an account yourself and contact me privately to get edit rights for the wiki.
Best regards, and I'm looking forward to any further updates.
Regards, Harald