Resolution changes after startup/login

You did not specify whether you saved your settings to the X configuration file (/etc/X11/xorg.conf) using nvidia-settings. That should solve this. Just open nvidia-settings as root:

sudo nvidia-settings

Then, choose the right settings and click on the "Save to X Configuration" button:

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If this does not work, there is something else overwriting your settings. Probably your desktop environment. As a workaround, you can use this script:

#!/bin/bash

sleep 10
xrandr --output DVI-D-0 --mode 1920x1080 
echo "Script was run" 

The sleep is needed to make sure that the Desktop Environment has finished starting before the script is run. That way, you know that it will be run after the DE has reconfigured your screens. Make the script executable and add it to your startup applications. That should do the trick.