"Deck 22 according to FJ is 2 decks below the hangar deck, IIRC since FJ layed out a 24 deck ship. In anycase, it sounds like you're just borrowing the visuals from the episode but not the deck layout according to dialogue - which is your prerogative
Again, I find this statement of the blue alien slave of Slar, the Gorn (on speed), to be inconclusive at best. I don't know what's going on in a head of this
Gorn species, but maybe having different main deck numbers and engineering deck ones was simply too much for his reptile brain, so he told his slaves to number the deck levels in an FJ scheme for their scavenging purposes.
In the audio commentary the producers admitted they had taken several artistic liberties and the aft photon torpedo launcher of the Defiant definitely falls under this category but served the story which is basically "Pirates of the Tholian seas" and instead of cannonballs they used photon torpedos (the infamous "Hornblower Effect", again).
Where I can't seriously disagree is the aft phaser. In "Arena" there is a clear intercom report to the captain that the "aft phaser" of the Enterprise is ready (I assume the ENT production people rewatched the episode because of the Gorn's participation, noticed the "aft phaser" report and then decided to visualize it). Frankly, I always had problems with the window under the stern dome to be the flight deck control room. Once the shuttle reaches the critical landing phase - it disappears from the sight of the flight deck controller.
Now, with this ENT episode it rather looks this is the aft phaser control room which makes more sense, IMHO.
And regarding these energizer / reactor walls on the Defiant in ENT there might be a better explanation. Since the Defiant appears to be a younger ship than Enterprise these walls may simply be the next generation of these energizer / reactors that usually stand around in one of Scotty's engine rooms.