> 1. How to avoid the automatic visit to tty7 and the execution of GNOME
>    Display manager?

If I recall correctly, something in /var/lib/gdm is notorious even in other 
distribution for its ability to call GDM when not asked. The usual advice was 
to rm -r the directory. DO double check this advice, as I do not trust my 
memory on this one.

You could also go to the GUIX repository, find the file with the definition of 
%desktop-services and copy the variable definition directly into your file. 
This way you are able to freely inspect and modify the variable to your 
liking. This is what I do with my changes to default data.