I recruited my beloved because many hands were needed; one for reset tool, one for power lead, one to hold modem, one to hold iPad with instructions and keep encroaching cats out of the way. Used simplified procedure, solid red light. Success!
Got in, loaded a master config. All done.
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Is there any chance that I could possibly have got into this trouble somehow by doing something that caused some kind of persistent state to get altered or deleted so that the device got into a borked state but where that bad state information was outside the normal xml config file?