I passed the CSSLP earlier today. I don't think you can take anything other than your ID, the key to the locker that holds your personal belongings and a pen/sheet for note-taking. But a dictionary is probably not going to be allowed. You might want to call ahead and specifically ask.
As for scoring, I don't believe CSSLP employs the domain specific scoring. The poster on the other thread misconstrued the proficiency levels sheet he got after failing. It is just to inform you how you are doing in individual domains so you can tailor your prep for your next attempt. He/she probably scored quite low on the domains they were showing "Below" and that contributed to a less than 70% score.