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To tell you if your CTR isgood or not it depends on your site some of our technical sites average a much higher CPM and CTR but get just a couple of hundred page views.
But obviously there are practical limits, because Google most likely is going to look carefully at sites with very high CTRs coupled with very high EPCs! Wouldn't you, if you were Google?
I've seen people report eCPMS of $200. They might have been making that up, though they usually acknowledged these were on channels with little traffic.
On the whole, I think you can expect that as traffic goes up, eCPM will tend to go down, so traffic is another thing to consider. Still, I'd rather have a site with an eCPM of $5.00 and 100,000 pageviews daily than one with an eCPM of $25.00 and 10,000 pageviews...
I don't know what's "wrong" with your site's keywords. You aren't earning much from AdSense, but that doesn't necessarily mean that there is ANYTHING wrong with your site or your keywords. Unless of course the only reason you set up the site is to make money.
Build a site with useful information in a well-focused area. Don't put ANY ads on to start with. Keep adding content and getting links, and maybe when you get to 1,000 visitors a day, put AdSense on....