Herewith my email:
I think what is below will answer most if not all the questions you asked. I'm sorry it took me so long to reply. I'm ill and not able to do much. But here are my answers keyed by number to your questions.
1. A Key element of Barbourite and Watch Tower theology is the concept of Spirit Bodies. While the exact nature of a spirit body is unknowable to those in the flesh, some of its abilities and nature are revealed in Scripture. You will find a good discussion of Spirit Body doctrine in Barbour’s Three Worlds. It’s available online.
A spirit body’s natural state is invisible to humans. Spirits are in Biblical terms “flames of fire” and dwell in God’s presence where they see him as he is. So Christ as a “life giving spirit” is exactly as God is, his very image and likeness. (Heb. Chap. 1) He is glorified to God’s right hand to dwell there forever.
Did Russell believe (after 1881) that Jesus was on earth but invisible? The Watch Tower speaks with a conflicted voice. He seems to have believed that Christ would rule from Jerusalem but he also seems to allow that his rule from there would be through earthly representatives and his presence there would be represented through some symbolic means akin to the light above the Ark of the Covenant.
2. Russell dated the parousia to 1874. He believed that Christ assumed Kingly rule in 1878. He believed the heavenly call ended in 1881 with the start of the heavenly resurrection. These ideas were based on time parallels with ancient events. The time parallel arguments were accepted based on confirmation bias rather than scriptural precedent. There was no other proof.
3. You will find Russell’s explanation in Food for Thinking Christians. Full text is online. Also some brief ZWT articles such as one entitled Optomi (Greek verb for “to see” in the August 1881 WT. (All early issues are online.)
4. Prior to 1879 Russell believed as did Barbour. Later he published without comment an article by L. A. Allen that suggests a totally invisible presence. That article started a behind-the-scenes discussion that culminated with a doctrinal revision in Food for Thinking Christians.
5. He gave up believing that Christ was present. He continued to believe in a future two-stage, partly-invisible presence. Barbour, Russell and Witnesses would see applying the word “rapture” to this event as a misuse of the word. Rapture implies a visionary experience. Translation and resurrection are “real” rather than visionary events.
6. Yes, by the end of 1882 he gave up that view.
7. Barbour did not introduce Russell to the idea of a two-stage, partially invisible presence. He tells us that it was his prior belief and that he met the idea in Seiss’ Last Times and other places. Barbour convinced Russell that it had occurred in 1874.
Russell was distressed by Barbour’s deflection and deeply troubled by it. But he did not doubt the truth of their shared doctrines. Russell’s belief was that a once revealed truth remained truth despite others’ doubts.