so your screen problem is only that you have to change your resolution after every startup right?
If you didn't uninstall your Catalyst driver properly, you have a xorg.conf file. You can use this file to configure the screen resolution. Before you change anything it is maybe a good idea to create a backup of the file:
cp /etc/X11/xorg.conf /etc/X11/xorg.conf.bak
Otherwise, if you don't use AMD's Catalyst driver you can create a xorg.conf file with following command
But this command works only, if you don't have the xorg-server running. So use this command in linux console mode. If you add 3 to the boot line it will boot into console mode.
below Section "Monitor" you can add:
Option "PreferredMode" "1280x960"
(1280x960 is a example for the resolution, just use a resolution which is best for you monitor)
and below Section "Screen" -> Subsection "Display" add Modes "1280x960", so that the SubSection "Display" looks like this:
Viewport 0 0
If there is any error in the file, xorg-server cannot start correctly. If you can't find the error in the file you can use your backup file or remove /etc/X11/xorg.conf