Hello there. I'll try to help you out today. For the first issue, monitor brightness: check out the attached file. Pages 18-20 describe how to access the menu, page 20 actually mentions brightness.
For the facetime camera, presumably this is a USB connected device. Have you made sure the cables are attached and tried unplugging/plugging it back in? have you also tried rebooting?
Does the light next to the camera come on? Usually web cams will have a small light to tell you when they're active. If facetime sees it (which it seemingly does seeing as its an option) then its odd that its not working. You may have a defective unit, or your monitor may need to be power cycled. its also possible that there is an option in the monitor settings to enable or disable the camera.
This may sound odd but are you certain there's nothing blocking the lens of the camera? a small sticker or spot of marker perhaps? if you look in can you see the actual sensor? (a smaller reddish or greenish circle within the lens)? It sounds like the camera itself is dead. if the Mac recognizes it, and the light comes on, you should have a picture. You could try it on a different PC or computer to be sure, but you're probably looking at a defective unit. If the monitor is under warranty Asus should replace or repair. If not, it may be most inexpensive to just purchase a small external camera.
could you kindly provide feedback on my service if you're all set?