I don't want to tell you what to do, but if I were you I would hold off on anything like uninstalling WP just yet. Based on what you've said I don't think it will solve anything for you, just cost you time which is money.
I've read a bit about earnitup but not used it myself, so don't really know how likely a suspect it is. I'd pull it since it's one of the variables in play. And I"m pretty confident wp super cache is not a culprit either, but I'd encourage you to keep thinking of what other changes you've made recently - and I don't just mean plugins or code changes to your site. Based on your @dsense impressions dropping so bad, it sounds like someone on the web has slapped your site or is dancing you around (read about the Google Dance? you might want to).
Have you been doing any marketing/promoting/backlink building or anything else with the site in question lately? Sometimes campaigns can be like boomerangs - sometimes they hit the person you threw the boomerang at, sometimes they spin back around and hit you.
I know it's frustrating to see such a traffic drop. In the past week or two, one of my AB's has taken off like a rocket, but one of my other ones has dropped like a....well, like a rocket that launched successfully but then started to disintegrate higher up. Figuring out traffic swings - up or down - is part of the challenge, sometimes it's fun, sometimes it sucks.
