What is the CMS the site is on? If wordpress there is a pretty good plugin that use the google analytics api to properly inform google of bounce rate, it took mine down from 35% to around 11% in 2 days.
Obviously that will help your SEO.
Have all spammy backlinks been removed?
Have you checked in Webmaster Tools?
Less likely to be meta keywords than SPAM or DC.
Both are easy to fix. Google can take a few weeks to acknowledge spam removal though
