It is after midnight here in Belgium. OK, in that case you really need to check Branch aware as well. The solution I told you is for the content slides, but if Branch aware is checked, normally the last 3 question slides wouldn't be taken into account for the users that do not take the addendum. The score slide has to be at the end, after all question slides. And the jump to the score slide should work for the non-addendum users and show the correct amount of questions and the correct score. Must tell that I didn't check it out extensively in CP7, it worked in CP6 and 6.1
I can only recommend now to add a text container, set for the rest of the project, in which you can track some quizzing system variables like cpQuizInfoPointsscored, cpInQuizScope (you should remain in the scope from the first question to the last one in the addendum).