Thanks again, Ken -- I really am very grateful for your answers here.
I'm confused about the original circuit vs your current recommendation. The schematic on your web site shows a 150k resistor while the PCB I have and the BOM on your site indicates 47k. Which do you recommend, in conjunction with your choice of a low current LED and 4k7--10k current limiting resistor?
Many thanks once again. I hope I can get the thing working after all this pre-build planning...