Being a pinko myself, I've got kind of a vested interest in 1930s radical politics, I think there's a lot we can learn from the period that got erased from the received-history of the post-McCarthy era.
I was raised a Methodist myself, but am a product of the "Social Creed" Methodism that came out of the Progressive Era -- if you go back and look at old editions of the Book of Discipline, you'll see that that the Social Creed a hundred years ago was far more lefty-radical than it is today, with specific clauses endorsing the right of labor to organize, wage-hour laws, the abolition of child labor, and all such as that. Quite a few thirties lefties came out of that era -- Genora Johnson, the "Joan of Arc of Labor," who helped mastermind the Flint sit-down strikes of 1936, was once a Methodist Sunday School teacher. So there was a strong tinge of radicalism in Methodism by the early 20th Century, which was very much at odds with the older, more rural sort of Methodism.
Rutherford's personal political trajectory fascinates me. He seems pretty obviously a product of late 19th Century populism, which although it had nativist aspects that in today's context would be considered right-wing, the whole Farmer-Labor movement echoed quite solidly down thru Fighting Bob LaFollete in the 1910s to the 1930s in the form of Floyd B. Olson, the Farmers' Holiday Association, and finally the CPUSA-led movement for a new "Farmer Labor Party" in 1936-37. If you approached the typical Witness of that era and handed them some CP pamphlets with the covers torn off, I think that they'd most likely approve of more than they'd disagree with. If anything, Earl Browder -- who was also raised a Midwestern farm boy -- was far more moderate in at least the presentation of his views than the Judge ever was.
As far as Russell is concerned, from my own political perspective I found a lot that was interesting in "The Battle of Armageddon." I read it a long time ago, so I can't quote you specific passages, but I remember being left with an overall impression that he wasn't unsympathetic to the basic concept of socialism.