I am sorry, but your screen is not affected by kitkat.
What you are looking for is a dark background and the brightness slider. and/or a new battery
Dude I have tried almost all KitKat ROMs I also got new battery and I always set black wallpapers and brightness level to 0 still can't get 3 hours screen time that's why asked for best battery KitKat ROM and I'm using a OEMbattery which cause screen flicker after 10%
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