Hello Volker.

You should use a submit data connection for creating a standardized method
for saving.  Submit is blocked on validation errors where the save function
is not. Then go into form options and disable the user's save and save as
abilities.  The printing is a bit tougher to control but you can make a
specific view for printing and then either put some text that states it is
not a completed form which hides once all of the fields are validated or make
it obvious in the view that dat fields are missing.