WoOopS! I tried doing it on your website and it didn't work, so I realized I messed up on my explanation after doing some research. I didn't exactly do it as I said, so scrap that. Here's how I did it:
When you go to "Settings" > "AddThis Share" in your backend panel, you have several options to choose from, on the top and on the bottom. What I did was choose "Custom buttons" for both top and bottom. An empty box will appear for each one, in which you can paste a generated code that you can customize on one of the links shown there, called "AddThis.com Sharing Tools" (exactly this one). On that page, I chose exactly how I wanted my buttons to show (you can take a look at the "Preview" box). This is pretty cool, because you can add additional buttons that don't show by default (for instance, google plus). Then, I copied the code from the "Add to your site" box to paste it on the boxes that appeared after clicking on "Custom buttons" earlier.
Although it may seem tricky, it is the best way to customize the buttons. When you save settings, the button code that you pasted on the boxes will be the one that will show on all of your posts/pages. So, if you paste that exact same code on the posts that can't show Addthis buttons, it will be as if the Addthis plugin worked :D . I, for instance, wanted buttons on the very top and bottom of my posts/page, so I pasted that code twice, one on the very top and another one on the very bottom. Simple, right?
Yeah, that's what I meant. Sorry for the confusion :D