bkklift, this is just a rough guide, its just a sliding scale with unfortunate labels - "over fat" aagh.
Two months ago I was 22% and I don't think anyone would have described me as over fat - I seem to carry the weight quite well although I did feel I needed to drop a bit.
I've only just started to use calipers and I'm still trying to get a feel for where in percentage terms I'm most comfortable.
Like you said calipers are very subjective and sometimes you get big discrepances between measurements. That said over long term you can track reliably with them as the odd dodgy measurement seems to average out i.e. the trend of a number of data points is either up or down. Its all relative at the end of the day.
As for yourself, looking at your pictures you look very lean and you are obviously making impressive strength gains so why worry what the chart says.
By the way this is all second hand info, this is where I found the scale etc...
http://www.bodybuilding.com/fun/drobson98.htmhttp://www.tmuscle.com/article/bodybuilding/the_truth_about_bulking&cr=