From what Ive experienced with Fastclick's there payouts are VERY minimal and no where near compare to Adsense revenues. Also, it's against their TOS to place Fastclick ads on forum pages.
Sometimes placing your ads in different positions on a web page helps. Also you say you are only running the ads on 35 pages - that's not many pages to earn lots of money from. Have you considered increasing the coverage across your website? If you're finding a problem with relevancy you could always change to another service such as searchfeed.com whereby you can specify the keyword terms. In my experience - cost per click is lower though.
Hoang Haven't you answered your own question on the other thread where you asked about a code? "Please tell me, because I don't want to be suspended by Google"