Too late now, but as a warning to others if you install a different OS some features can go missing.
The BRIGHTNESS control for example might be an issue with the laptop manufacturer using slightly modified graphics drivers to connect to the laptop software for keyboard control.
Thus it's possibly the graphics DRIVERS that are the problem, so it may be necessary to use drivers specifically from the laptop site not Intel, AMD or NVidia (as applicable) directly.
However, if possible it's usually preferable to use the default drivers (for the GPU, not laptop specific) so if they do work natively, or there's a SOFTWARE package to be installed that works do that.
(In some cases you may need software from a different OS like I did with media card drivers from Vista from my support site after installing W8)