Your first picture is from galley view right? And you’ve enabled condensing of divisi I presume.
The niente doesn’t look missing, it looks like it’s appearing above the staff - try deleting the dynamics for the lower staff and copying them again from the upper staff. If they’re not exactly the same, Dorico can’t condense them into one so shows both. If that doesn’t work, share at least a cut-down of the project for someone to investigate/play around with.
Or, do you mean the “n” isn’t showing? That’ll be because you’ve e.g. changed the niente style in one layout but that’s not carried across - select them in the layout where they look right and propagate properties; or change the style with the property scope set to “Globally”.
I presume the voice column offset is because the 2nd divisi, in the lower voice, has a harmonic that’s the same pitch as the stopped pitch in the 1st divisi; the noteheads aren’t the same, so they can’t overlap. If these harmonics can be played as natural harmonics rather than artificial, that would eliminate the 2nd notehead and might allow for neater overlap.