Hello, I hope this comment answers the main points: https://www.reddit.com/r/AskHistorians/comments/dhjg5a/comment/f3p3bd8

To try and answer the extent of camouflaging, Bormann issued orders in Autumn 1942 for new propaganda directives that would counter « rumours of ‘very sharp measures’ taken against Jews in the east ». (Kershaw "Hitler" p.202) Rumors were circulating around this time of the shootings in the east. The following year Bormann ordered "on the Führer's behalf" that public discussion of "a future overall solution" [Gesamtlösung] to "the Jewish Question" should be avoided and it should only be stated ‘that Jews had been conscripted en bloc for appropriate deployment of labour.’ (www.ghwk.de) It's unknown if any "hard information" was circulating throughout Germany about the extermination centers like Auschwitz. (Kershaw "Hitler" p.203-4) But for the majority of German citizens major parts of the Holocaust were out of sight and out of mind. Likely due to guards agreeing to "unconditional secrecy" and keeping Sonderkommando's mouths shut. This isn't to say no information was circulated however, as the Munich ‘Special Court’ contains two references to the use of gas vans.(Kershaw "Hitler" p.204)

As for "fear" among the Nazi's - more particularly "Himmler or Hitler" - it most definitely existed. They were fully aware the German public wouldn't accept their activities. According to Kershaw the "Mayor of Mainstockheim" spoke for many when he said; ‘You don’t have to have anything to do with the Jews. But you have got to leave them in peace.’ (Kershaw "Hitler" p.206) This is why Himmler said the Holocaust was a ‘never to be written glorious page of our history’ - that is a secret to be carried to its grave.

Sources: Kershaw, Ian. Hitler, the Germans, and the Final Solution. Yale University Press, 2008. (See Chapter 8) https://www.ghwk.de/fileadmin/Redaktion/PDF/Konferenz/bormann-juli1943.pdf https://phdn.org/archives/holocaust-history.org/auschwitz/19440524-weisse/