I suggest taking things one step at a time. Your reports from SEOmoz may include tons of errors, but you can often fix tens or hundreds of these errors with one fix. I see some technical updates you can make to your pages that will help clean up the source code and perhaps make your pages load faster which will help.
A couple quick technical tips:
Clean up the inline CSS used on your pages. Use your external CSS files to hold this information.
Don't use relative URLs if you don't need to. You can fix a number of linking issues by just using absolute URLs.
Here's a helpful post from Paddy Moogan:
http://www.seomoz.org/blog/common-technical-seo-problems-and-how-to-solve-them
More to come later. Hope this helps!