Nice work. Thanks for helping me clear up some mental confusion. Your statement below struck a chord with me:
"I suspect he even believed the whole thing -- till 1914 came and went."
I wonder if Russell was so completely deluded that it hastened his death when his prophecy did not come true. We all know how in October 1914 he declared the Gentile Times had ended. He was dead by October 1916 at th age of 64. He could have calmed the cognitive dissonance by rationalizing that he forgot to account for the lack of zero year between BC and AD, gaining confidence that he would see the rapture in 1915. He must have been berated countless times for being a false prophet, probably even by people close to him. But he evidently left notes behind for the "The Finished Mystery", claiming to be the Laodicean Mesenger. The mystery is what he was really thinking.