I just looked at your site. You have not completed the integration. You need to do all the class additions to your stylesheets.
I never login through Photopost. I login through Threads and if cookies are set to / then Photopost reads it.
As far as login information did you happen to put a forum prefix in the config. If so this will cause problems. If your forum database prefix is the standard w3t_ you do not need to specify anything. Check in your Photopost database under settings #83 and make sure the forum prefix is empty if you use the default.
Login works fine on many sites and what little code you enter from this mod only affects stylesheets. The Header warning is a PHP warning setting.
I would look to your inability to login on the Photopost site as there are many many threads about login's not working between most every supported board. You can also contact me privately and I will help you figure it out. It is no doubt simple fix or setting.
