1. This thread should help you PhotoPost Enhanced vB3 Index Integration
2. I dont know what you mean by this? Your using the vbheader include which means we pull in the $header from VB3 It looks right to me when I see your site. Thats the same header as VB
3. There is currently no automatic language switching support in Photopost since for us to include that in our distribution we would need to include language support for every language every forum we integrate with. That is quite a dawnting task as we have a hard enough time getting users to submit user languages for the languages we support let alone translating new languages that some forums support that we dont.
The task of making it automatic is not that hard a thing to do. If you make a language file for Photopost in your language directory for every language your forum supports then you can post a thread over at the hack site http://www.photopostdev.com
since file modifications are not discussed at product support and I will see if I can post simply what modifications are needed to your vb3.php and pp-inc.php file to autoload the new language files you have based on the VB