Use the "Status Bar" to turn off "Safe Mode'. Pull down (swipe) the "Status Bar" of your phone. Now tap the "Safe Mode" button. This should turn "Safe Mode" off. Now your tablet will automatically restart, so that it boots up out of "Safe Mode".
If it won't work then either, then there is something wrong with the device. Perhaps a button is stuck. Which would explain the not getting out of "Safe Mode" and not turning off.