If there is a VGA port on your TV just use the VGA connector. If not you can purchase a USB to HDMI or VGA to HDMI adapter. The adapters go into the computers VGA or USB ports, and convert the output to HDMI.
Try blowing under the stuck key or keys with a can of compressed air, this should clean out any dirt or debris that are making the keys stick. If this does not work then the key mechanism may have broken and could need to be replaced. Though it is fairly difficult to break the mechanism in this way so give the can of compressed air a good try.
To increase the brightness of the screen hold down the "Fn" key and press the up arrow key. To lower the brightness do the same but instead of the up arrow key press the down arrow key.