Thank you for sharing your insight. Believe me when I say that I am only too happy to consider any reasonable suggestions and insights that someone may have.
Shorting the starter relay is what I believe my friend with the experience as a professional mechanic tried. Since the didn't accomplish anything at least now I can rule out the starter motor as the cause of this issue.
Acting on the advice of yet another friend who is a graduate EE, I undid the changes I had made to the right headlight as well as looking the associated wiring over for any indication that I could have inadvertently removed some insulation, but I could find no evidence to support that possibility. I connected the van to a fully charged battery pack and tried to star it, but this time, there were no clicks, whirring sounds or any evidence of life - EXCEPT I did observe that both of the turn signal indicators in the instrument cluster flickering rapidly. This flickering continued even after switching the ignition off. At that point, I disconnected the battery's ground lead. That gives me yet another lead to research. I love a challenge, there can be no doubt, but this is beginning to border on the absurd!
Hrmmm....I wonder if I can find an Amish person, that would swap me even-up for a horse and buggy?