It is updating! Not sure what I tried this time different, but something, or a combination of things got it to initiate the update. I tried formatting the card from the GO app, which someone suggested elsewhere, then I cleared out the P3 files on the SurfacePro and downloaded the update again. Dragged and dropped only the BIN file onto the newly formatted card, and it worked! I think the only thing new here in these steps was using the app to format the SD card.
Oh well, it is updating and that is what matters.
Thanks guys for all the help and suggestions.