Hello Martin,

I have some new information that may help with problem 3.

Quite often I run emacs on one machine and control it from another over my
small home network.  I am updating my operating systems as well as
updating emacs.  One attached screenshot shows the display on one machine
(Mneme) running Linux Mint 18.1 when accessing emacs 25.1 running on
another (Thalia) running Linux Trisquel 7; the connection was by X
tunneling over ssh.  The display shown is repeatable.

The important thing from our point of view is that the screenshot shows
the problem 3 effect.  Furthermore, it shows the effect with the main
emacs frame as well as with a popup.  The cream coloured area is emacs,
but this should be covering the whole of the large grey area; I start
emacs with the entry (fullscreen . maximized) as part of its
initial-frame-alist.  The maroon coloured area is part of a subsequent
popup, which should be covering the smaller grey area, which is the popup
frame.  It is clear that the text in the popup is truncated both
horizontally and vertically in precisely the way that I have reported
before when running and displaying on one machine.

The other screenshot shows just the main emacs frame; I put a find-file
line in my .emacs; the file contains the numbers shown.  The line width is
102 and I do have this line in my .emacs:
(setq emacs-lisp-docstring-fill-column 100).  However, at fullscreen, I
can display two windows side-by-side at this width, and the docstring fill
column probably is a red herring.  By watching the start-up it appears
that the cream coloured area is the same size as the initial size of emacs
before the (fullscreen . maximized) takes effect.

I am hoping that these screenshots will throw some light on problem 3.
The key question now appears to address why the main emacs frame is not
filled properly, my popups can be eliminated as the cause of the problem.

David