I'm rated 1218 and my percentile is listed at 59.7%; seems (very) high, expecially since my rating was about the same last week and percentile was about 45%.  also I see the average rating on the site is about 1340 so am I correct that 59.7 is not right?

I suspect it has something to do with the "Facebook Chess" merger. One would expect many of their ratings to be low as that is not a dedicated chess site. Maybe the site stats haven't kept up with these developments. I'm just guessing.