MacBook Air: How do I select primary display to mini Display port?

I have a Model MacBookAir3,2 (MBA) with a Mini Display Port. I just hooked my output up to a HDMI port on my SONY TV. (I also selected to have the sound directed to the HDMI device.) The TV now behaves like a second monitor. However, I don't know how to select it to be the only monitor. (Of course, I can mirror the original screen, but that's not the goal.)

Secondly, to watch a movie, I'd like to be able to close the lid on the computer but continue using the feed to the TV. There are two issues: keeping the MBA from sleeping, and keeping the feed running. Seems as if I can only do that if my MBA is paired with an external keyboard (and setting the sleep settings to Never.)

The only workaround I can think of is simply to turn off the backlight for the MBA screen and not close the lid.