John, while I have previously given RD cheese my blessing as being a constituent of the upper echelon of cheese that is the wholesale realm, I don't think you've ever mentioned the pre-shredded part
Friends don't let friends use pre-shredded mozzarella
It could be a variety of factors, but I think the general consensus is that the anti-caking starch prevents the cheese from melting as well as non pre-shredded brick. I'll concede that there might be a wholesale cheese with the necessary fat content and meltability to overcome the anti-melting aspects of pre-shredding, but, right now, I haven't come across one. Until I do, either buy RD brick and grate it yourself, or, if you absolutely have to go with grated, go with the inferior cheese workarounds such as drizzling oil or sticking with pepperoni.
You could dial it down to 475, slow down the bottom, and get that extra 30+ seconds of top browning using just convection, and that would put you in the 5ish minute realm (possibly closer to 6), or you could stick to 500, use some intermittent broiling and do 4. Both are good. Convection is a big golden brown contributor, so the 5ish minute bake will be much more golden brown, while the 4 minute bake, with the broiler, will be more contrasty/a little more charred on the top. Both will be great pies.
As Craig pointed out, less cheese is something worth trying. For now, though, I'd really like to see what this quantity of cheese looks like with more color. There's no hyperbole when I say that, with some more top color and golden brown cheese, the pie above could rank in my top 20 favorite NY pies I've ever seen on this forum. Considering the time you've spent here, that's pretty amazing.