global.cfg has almost nothing to do with your device's resolution and data.zip in NextGen is designed from the start to work with all types of resolution. iGO automatically adapts to your screen
Here I want to do the opposite, to fix and set a low resolution, because then the display will be larger and the names of the streets will be visible.

Otherwise, iGO by default shows only the main streets and those that are in focus (which is logical because otherwise you would have a forest of overlapping data on the screen). So displaying a lot of the streets is not possible without changing the code of the application itself.

And as for your screenshots - it can't show something that doesn't have a name or it is not in the map database.
Either change map provider or complain to him
But first check if there really are names of the streets in those rural areas and are they streets at all.