I am now certain that I know the cause of the belt failure. I am quite sure that the belt would have lasted through the event if the variator hadn't failed. The variator failed at the bushing around the shaft. The hole that wraps around the bushing enlarged irregularly creating a wobble and shake. This created vibration and heat that I could feel. When we cobbled together pieces to fix it, we reinstalled the bad variator that shredded the belt after less than 30 miles on day 10.
I had intended to bring a new variator on the ride but waited too long, and decided that this one, with less than 10,000 miles on it would be OK. I also shouldn't have put Dr. Pulley sliders in it before the run. I have had two failures in variators, both times with Dr. Pulley sliders inside.
Next time I will come better prepared to make repairs. Tools, spares and the ability to do my own work on any potential problem are in the works. I am buying parts now, including a gear puller and other specialty tools. And I am getting comfortable with the work itself. Boris has agreed to help teach me, so I will be ready.