Very nice!
I like your speculative left-hand wall of AC, although in fact we saw that wall in 2 episodes, should you find them useable:
http://tos.trekcore.com/hd/thumbnails.php?album=60&page=2
http://tos.trekcore.com/hd/thumbnails.php?album=53&page=5
Of course, those were also the episodes where the door to the room when from being a double pocket door to a single, so make of that what you will
This is not one of the standard corridors, it's only about 6 feet wide (instead of the standard 8 feet). It was likely constructed specifically for that scene.
You may be remembering the work done by
@feek61 on the Auxiliary Control Room. He postulated the location of AC similar to where you described:
You are correct - the closest FJ came to was the "spare bridge" which was a simplified version of the main bridge design. This is very likely because there were no AC stage plans for him to draw from!
In terms of location on board ship, it was called out as being on "Deck 8" in
I, Mudd.