In Reply 6, you mentioned only two sizes, 12" and 16". I assume that the medium is 14". Is that correct?
As to your basic question, there can be several possible factors for a crust being too chewy. It can be because you are using a high-gluten flour, which has a relatively high protein content that can naturally result in a chewy crust. Some pizza operators use a weaker flour (one with less protein) or blend the high-gluten flour with a weaker flour in order to reduce the chewiness. A chewy crust can also be caused by a dough that is underhydrated for the particular flour used. That is why I suggested increasing the formula water from its current 52.9% to something higher that is closer to the rated absorption value for your particular flour. If a dough is overkneaded, you can also end up with an overly chewy crust. That is one of the reasons why I suggested that you use the dough preparation and management protocol as set forth in Reply 18 at http://www.pizzamaking.com/forum/index.php/topic,7499.msg64554.html#msg64554
. I believe that that protocol should be at the center of what you are doing, and adjust it if necessary based on your particular results. You might also end up with a chewy crust because of insufficient leavening, that is, too little yeast. That is why I suggested using more yeast. Lowering it to slow down the fermentation process is not the ideal approach in my opinion. It is better to get the proper amount of yeast for the window of usability you are after and to control the temperatures to get the finished dough temperature in the optimum range as noted below. If the pizza is baked too long and the crust dries out too much, you can also end up with an overly chewy crust.
If I think long enough, I perhaps can come up with another reason or two for getting an overly chewy crust, but the ones given above are the ones that come to mind at the moment.
Overall, what you should be looking for is balance in the formulation, including temperature control. That means having the right hydration and the right amount of yeast. The rest of the ingredients appear to be in order for the style of pizza you are trying to make, so I don't have any suggestions as to those items. With respect to temperature control, that means controlling water temperature to get the finished dough temperature in the right range (80-85 degrees F) if you are using dough boxes and a cooler (you would use a lower finished dough temperature if you are using trays covered with bags).
I hope that you will keep us posted on your progress.