Hi Barry,
Regarding your first question on the relationship between the GPIO_SET_DATA45 register and PIN 9_14.
Here is how I did it:
Found that P9_14 is GPIO0_93 using showpins.pl:
Saw Table 12-12 GPIO I/O Signals (continued) in the TRM on page 1383.
^^^ This is where the 
came on!
Cross-referencing Figure 2-25 in the TRM J721E_registers4.pdf page 87,
Found that bit 29 was _93.
Doing this GPIO toggle exercise, I realized that for BBAI64 baremetal you have to get all the tech info into your brain and then the linkages of the concepts just kind of filter out of your subconscious. – that is how it seems to work for me anyways.
Looking forward to seeing how you make out with your experimentation. If we get enough brain power on this thing, we will get it figured out 
Not sure why the old Beagle veterans haven’t engaged on the AI64… maybe they are just being stealthy 