Quit blinding yourself!
No wonder you've been losing sleep - you might as well be shining a flashlight in your face. Your backlight may work great while reading outside or while the lights are on, but as soon as you turn the lights out, your eyes (and anyone else's in the room) are still being bombarded with light.
With Dimmer installed, you can turn your screen brightness down even further. From 100% to 30%, your normal backlight will control your brightness, and below 30%, Dimmer takes over and lets you virtually dim your screen beyond what your backlight can do.