guero If your games window size was 480*800 just set it back to 480*800.
What you want to do first since your window and layout size are the same is extend your background layers tiles, and or sprites much farther past your window size in all directions. This makes your background fill all resolution sizes.
Then extend each layers tiles, and or sprites to match your newly extended background as needed.
Also set the Parallax to 0 in the Layer properties window when Unbound scrolling is set to Yes on certain layers.
Other than that your other settings seem correct. It is hard for me to guess since I cant see your project so you might have to play around with it to get it looking right. There are no rules to this method it is just a lot of trial, and error until you get it working.
Basically you are just trying to create the illusion that your game is in full screen on all devise resolutions. I know this all seems confusing but once you get your game working your next one will be easier because you will just build it differently right from the start.