If it will help, I can reread everything on the RT pizza and dough processing. Since I last worked on this project I have had more opportunities to reverse engineer other dough formulations so I may be a bit smarter now. It would certainly help to see some close-up photos. It would also help to have a detailed description from you of the typical RT crust in terms of its thickness, texture, color, crumb, etc., to the extent that the close-up photos don't show these characteristics.
When I revisited the RT dough ingredients list this morning, and the dough formulation I posted, I saw that salt was just below water. I used 1.75% salt since that is a common amount without making the crust overly salty. From the formulation standpoint it could be increased to about 2% and not affect the saltiness of the crust all that much, and that would allow one to increase the shortening to about the same value. However, I think that there are other factors at work that may be more important than the amount of salt and shortening or any of the other ingredients for that matter. Flour selection may be one such factor as you noted but it is also possible that the biscuit quality comes from the way the dough is rolled out, including re-introducing scrap dough into the process.