That is one loaded question!
For the on-page, I would recommend testing out SEOmoz's on-page optimization tool: http://pro.seomoz.org/tools/on-page-keyword-optimization/new
It seems you have a fair amount of relevancy assuming your main keywords are "fake diplomas" and "fake degrees". Nothing on your site seems to be a glaring issue that would 'cause you to NOT rank, besides that "links" page. I would take that down ASAP. Also, adding a blog section will help with reoccuring fresh content. Something Google loves.
All of your onsite effort can be next to meaningless if you were hit by Panda and/or Penguin. From looking at your backlinks, it appears as though you may be experiencing some issues with relevancy, low-quality links and/or heavy keyword anchor text.
Have you been using blog networks like Build My Rank or Distribute Your Articles? Have you been spinning content? Have you been buying Fiverr ads that are claiming they'll get you 10 .edu links for 5 bucks?
If so, you're going to want to reconsider your link building strategy and focus on higher quality links from more legitimate websites.
Being a guest posting company, I would venture to guess that link building is going to be tough for this industry, even if it is a 100% novelty item. Just focus on more legitimate link building, vary your anchor text like crazy, try to have the link JUST be the URL and watch your Webmaster Tools. If you have gotten an unnatural links warning, you might just want to check out the new link disavow tool.
I hope this helps, you have quite the road ahead of you but it's nothing unattainable.
Kevin Phelps
http://www.linkedin.com/in/kevinwphelps