I upgraded my modified 7.5.6 forum to 7.6 and have a few display issues that may be from my mods, but I'm not sure.

1. Forum is left aligned on screen - would prefer it centered - http://j30.us/ubbthreads/ubbthreads.php/forum_summary.html
2. The forum width is ok, but when a topic and some menu options are opened, the width decreases making the center column too narrow.
Here is a narrow problem link - http://j30.us/ubbthreads/ubbthreads.php/forums/10/1/the-boat-sails-and-equipment.html

Any idea what file I edit in order to correct this problem?