Thanks for your comments!
Finally I have a major update - all the issues are sorted out and the tube is finally working as it should be. We have managed to get perfect parameters of the tube, similar to those of old nixie tubes (breaking voltage, minimum current for the glow, etc.)
Here is one photo of the tube working:
- I took this photo with the phone camera so the digit glow is oversaturated, but in person, it looks much more natural and more even (I'll have some professional photos soon, as soon as we fin all in the prototype case)