My room conf is 16 x 13, with the front wall partial to a hallway (see front pix)....
I don't know if this is feasible, but you might be better off turning the room around - putting the speakers/TV where the seating is, and the seating where the TV is. Having that open hallway right behind one of the speakers is going to give you some oddish echo problems on that side. It might not be enough to bother you, but then it might.
You can probably use 1" OC on the reflection points. If the door is a reflection point, yes you'll want to cover it.
If you've got a subwoofer in there, then yes, bass trapping is going to be important. Ethan will certainly be full of suggestions. You'll want to treat all 8 corners if you can.
You might want to move the front speakers out into the room a little, and move the rear ones closer together, but that's something you have to experiment with.
Invest in popcorn.
