Nick, I think you need to look at few things a little differently.
Whether you're looking to recreate the NY slice from your childhood or the slice you went out and picked up last night, sourdough starter isn't going to get you there. Sourdough has absolutely no place in NY style pizza. If you're getting this idea from Jeff Varasano, Jeff's a very smart guy, but, when it comes to starters and NY pizza, he's dead wrong.
I'm not knocking sourdough. If you want to get into that eventually, it can make a great tasting crust. But it introduces a lot of textural variables that can wreak havoc for a beginner with particular goals such as yourself. For now, lose the sourdough. And lower the salt. You might find Neapolitan pizza with 3%, but not NY.
The AP flour is just too low protein for NY. Ideally, you want bromated 12.7%-13.2% protein flour, such as Spring King or Full Strength, but that can be especially difficult to track down. King Arthur's Bread Flour (KABF) is not quite as good, but will produce far better results than AP.
Tell me about your stone. How thick is it? How big is it? Does your oven have a broiler in the main compartment or is in a separate drawer?