I am not certain that I am qualified to answer all of your questions - some of your post may have to be responded to by the Webmistress. Here is what I know, in response to your questions and statements:
Is there only one of the Board members on the Forum? There is no Board, so I think you may be referring to the IGKT Council? I am a Council member and Editor of Knotting Matters.
Isn't everyone who pays their dues a "Full Member"? No - the members of the Forum are a separate bunch from those who have elected to be a member of the IGKT. Some Forum members are also IGKT members but not all Forum members are IGKT members.
Although not strictly posed as a question (no query mark at end of statement) your reference to Forum member standings absolutely has to do with their number of postings made. I am uncertain as to where it is laid out as such, but I know it to be true. More postings equates with higher standing. A Global Moderator is one who has earned the title, based on their demeanor and their knowledge, and has been asked to look at the boards (the posting areas) on a regular basis to ensure that people play nicely together, admonishing where necessary, guiding, cajoling and whatever else is necessary to keep a semblance of order whilst not disrupting the flow of excited speech (provided it is not derogatory, defamatory, improper or otherwise not acceptable) - in short, to moderate the Forum.
Hope this helps!