The quality of the backlinks may not be very good. Whenever you are developing backlinks of your website, you will have to keep in mind that you will stress more on quality rather than quantity. You will have to understand the purpose of backlinks and that is link popularity but it should not be done unnaturally or i would say unethically.
While developing backlinks, you always have to make sure that you are creating backlinks from high PR and relevant site. Otherwise, Google would not value them as a backlink.
Google doesn't consider just the backlinks to rank your pages. It involves other factors too. Just imagine, how much traffic you have been losing as your website is down. It effects your SERP alot. That is why it is recommended to use 404 redirection for your pages instead of removing them.
As mentioned before Google's algo has over 200 factors to take into consideration .
They even recommend that we forget about PR and have removed it from the webmasters tool kit.
It is not just the number of links that you have , but the quality and how you are linking.
Keyword rich anchor text, relevancy..etc
PR is important to show the credibility of a website. Just to prove a point, how good your website is. It can needed if you are selling your website or you are trying to attract customers for link exchange etc.
If you are doing a link exchange, it is considered as black hat technique and it is never recommended.
PR won't traverse by no follow link. Back link count is not a matter. It depends on the parent page's PR. If you are getting single relevant link from PR 3 page it will enough to get PR2 for your page. PR also vary depends on no.of outgoing link from a page.
I guess, that might be a missing part on your website. Perhaps, your webpages are not optimized. You would need to do the on-page optimization as well. You may create inter links between the pages too.
I need to ask you one more thing about the backlinks you have created, do they offer no follow attribute or do follow attribute because Google will not consider them as a backlink, if it would be a no follow.PR is not about having few back links from high PR. I feel, its overall natural link popularity.
I completely agree that links from "bad" sources will cost you you ranking rather then improving it, and with PR recalculation taking time. Also, you'd be better off with 300 good links from good sources then 30000 links from just one or two. It is considered an artificial inflation and will harm your ranking.
If you haven't already, I would recommend to use the Google Analytics and diagnostics tools within we webmaster tools, - if Google has any issues with your site, it will be evident there. If you have any issues with your sitemap structure, or any other factors it will affect the ranking.
Absence of a result is a result, unless defined otherwise.