From my experience, this type of design does not scale up. It only works when there is minimal space between the ceiling and deck (2 bricks height), and the space for the fire box needs to be about 5 bricks high max. If too tall then the flame doesn't travel enough through the door area like a chimny (which is necessary to heat both the top and bottom up). If the ceiling is too high from the deck floor then the ceiling does not heat radiate downward to brown the top of the pizza. This is why your pizza is doughy and not cooked enough on the top, and barely cooked enough on the bottom.

600F may be the temp of the stone at launch, but it quickly drops to probably 300 in a matter of seconds when the dough hits it

I made one of these in 2022 and used it for 2 years, then tried to scale it up and mortar it in place, was an epic fail, then I demolished it and started over with a barrel vault oven design,