MacBook Pro 2011 having problems with sleeping and screen brightness after removing GPU drivers (it had failed)?
The first thing I would try is resetting the System Management Controller (SMS).

How to reset the SMC on your model of MacBook Pro


Shut down your MBP
Unplug the power cable from your MBP
For 10 seconds, press and hold at the same time the shiftcontroloption keys (on the left side of the built-in keyboard) and the power button
After 10 seconds let go of all keys and the power button 
Plug in the power cable
Switch your MBP back on