WMT questions on WMT questions on WMT questions

I've couple of questions about Google WMT's "search analytics" section, particularly I want to understand how these "positions" work. Ive read Google official guide on how to read these data and how to understand positions but after reading it a lot of times I'm still confused about some of it. I want to break down which parts confuse me and I'd appericiate if someone could help me to make sense of it.

Google official explanation how to understand "Position" metric

Position - The average position of the topmost result from your site. So, for example, if your site has three results at positions 2, 4, and 6, the position is reported as 2. If a second query returned results at positions 3, 5, and 9, your average position would be (2 + 3)/2 = 2.5. If a row of data has no impressions, the position will be shown as a dash (-), because the position doesn't exist.


My Questions:

1. "The average position of the topmost result from your site" -- for what search term(keyword) the average position of the topmost result? is it refereeing to these "queries" in my screenshot? because you gotta be searching for something to get page results in a first place, it just says "top most result from your site" but it doesn't say when I search what? my websites name? a specific term? or there terms listed below as queries?

2. "if your site has three results at positions 2, 4, and 6, the position is reported as 2" - Okay... makes sense!

3. "If a second query returned results at positions 3, 5, and 9," - Ok, here something else that I don't get it... WHY would querying the same term for the second time return any different position than for what it was the first time? if the first time it was at position for example 34, should it be there for the second time as well?

4. if you take a look at my screen shot besides these "positions" right next to each search query there is one main "avg. position" that is reported as 66.0 in my case, so what is this position about?

5. let's take of my queries as an example, the very first one "aweber spam", according to it's position report, it says it's at position 9, which means it should be the first page of google for "aweber spam" but it's not there, its not on the first, second, third and not on 14th page of search results, so what do I make out of this?

Thanks anyone who took the time to answer any of these questions :)