Glad you fixed the error.. it's a common mistake
As for adding the button to your existing module, it should be pretty easy.. though CB code is never terribly clean, unfortunately. In their code, you should NOT be putting the {JFBCLogin} tag in a PHP block. It should be outside of this.
Another option that may work well for you is to simply use a Custom HTML module. In the code area for that, simply put {JFBCLogin}. Then, you should just need to float this module position to the right of your existing module. That way, it's separate from the CB login stuff, but still near it.
Hope this helps some more, but if you need more specifics, we can probably help you with it. The JFBCLogin module doesn't have a horizontal mode, unfortunately. We've looked into adding it, but since we added the {} tag for the login button, it hasn't been requested much.
Good luck!