Has to be steel, or tinned aluminum. Can be cold or room temp when placing dough.
I have heard there is controversy about corn meal, that some folks say it is needed, other say not. I think you are okay either way. I will say, my favorite deep dish Chicago style pizza out here was Pizzeria Uno, but, only vaguely related to the Chicago family (enough to use the name, not enough to be part of the original). But, they used a buttery crust with semolina, not corn meal, and it was delicious.
I see you correctly covered the cheese with tomato sauce, normally, the cheese is on the bottom, slices placed in a layer or two, then meats, then veggies, then repeat is there is room. Add tomato sauce on top, layer it is thick, more like 1/2 inch deep. As you saw with yours, it evaporates as you cook it. By placing the veggies on top, they cook faster and braise in the cheese better. (incidentally, I did not learn any of this on my own, this was all told to me by people who worked at Pizzeria Uno and Zacharys, who do a stuffed pizza, not a deep dish).
Whip It Off, Chambers!
"perhaps...but then again...maybe not..."