For those having the backlight wont stay at level 10 bug, try the below solution:
1) set your screen brightness to level 10, and timeout to 1min.
2) now set your battery saving mode to 'always on'
3) then, proceed to your screen brightness menu, try to set your timeout time to 1 min. Note that your brightness is still 10.
4) lastly, switch off your battery saving mode.
5) reboot.
See if the above works. My screen brightness stayed at 10 even after multiple reboots.