Funnily enough they could, volksliste had 4 cathegories and actual German origins was not even necessarily needed. For example a enthusiastic nazi which lied a little could be easily signed to 1st or 2nd, someone married to a ethnic German to 3rd, and anyone really could be fit for a 4th as "racially valuable". Also don't forget that nazi racial policies were as inconsequential and malleable as needed.
Yes, as they did it mainly out of survival and wanting to “please their new masters” as the vast majority came from POW and concentration camps. Few were probably true ideological Nazies, they were just scum.
Doubt it, but possible. Most likely they were told an "abridged version", so to speak.
felt that Lebensraum was a good idea
Sure. How do you think Russia got so big?
felt elated at being described as subhuman?
Just like the modern nazis in Ukraine, they likely thought it wasn't about them. Blamed it on the Jews and godless commies (who were either Jews or manipulated by Jews). Here you'll say it's just supposition, but here's the thing, I live in Russia, and I had the displeasure of knowing a number of Neonazis personally. Classmates and such, you know how it is with groups you can't leave. That was basically their shtick. And those historical collaborators that weren't actual, fervent nazis, they thought they were liberating ol Vaterland from the ebil judeobolsheviks. Just look at the amount of "former" tsarist officers and aristocrats that had gone on to collaborate with the nazis.