Is it possible to force _admin or _edit to remain https. I know this is possible for just the login screen, but it this possible achieve this for all pages after the login?
There is no option in Matrix, but you can do this through Apache by redirecting all HTTP URLs with _edit or _admin to a rewritten URL with HTTPS instead. We've done it before but I don't have the Apache conf available to post an example.
Actually, I lie. I found a copy. These lines are in the virtual host for the Matrix system:
RewriteEngine On
RewriteCond %{REQUEST_URI} ^(.*)/_admin.*$
RewriteCond %{SERVER_PORT} ^80$
RewriteRule ^.*$ https://%{SERVER_NAME}%{REQUEST_URI} [R,L]
RewriteCond %{REQUEST_URI} ^(.*)/_edit.*$
RewriteCond %{SERVER_PORT} ^80$
RewriteRule ^.*$ https://%{SERVER_NAME}%{REQUEST_URI} [R,L]