Double check the "product" that you're selling. If its adsense, it could be ad placement related. If it's clickbank, maybe the product doesn't convert well. There's alot of factors.
Directory sites won't give much earning, webmasters are know about ads and not ready to click adsense.
It really depends on the nature of your site. Which kind of site are we talking about. Also adsense might not be the right way to go depending on your niche
It depends upon your site content and site design. May be you are unable to get good CTR and good CPM ..Here you have to work hard
You are mistaken. They also pay per 1000 impressions. Check your facts before posting incorrect answers