All the 'z-index' values for the Juicebox-Pro gallery are set in the 'juicebox.js' file which is obfuscated and cannot be modified so, rather than try to increase the 'z-index' values of the gallery components, try decreasing the 'z-index' values of your own web page components.
I notice the 'jquery.fancybox-1.3.4.css' file on your web page uses 'z-index' values starting at 1000 (and it seems to be the only CSS file to set 'z-index' values). Try decreasing these values (for example, from 1000 to 100 and from 1001 to 101, etc.).