1. "RE: unique client ip sessions?"
In response to message #0
In order to count as a session, a visitor must have at least one page view. Page views are all hits that are not GIF, JPEG, PNG, CSS, JS, and a few others If a particular client IP hit only "non-page view" files, then the hits would be counted, but there would be no sessions.
The determination of which hits are page views is configurable. There is a log filter in IIS named "Compute page views" which does this.