Your issue is caused because (by default, anyway) TweetMeme's script uses the URL of the current page. If you notice, all your posts show zero tweets, but they all also have the same reference ID (look at the status bar in your browser as you hover over the TweetMeme button) and the source code shows that they're all referencing your home page.
However, this should be easy to fix. Add the following line of code directly above the code you added to display the TweetMeme button and all should be well: