I don't know the answer to your question, but here are a few notes...
1 - The weights can be set to anything in your scenario, as long as they are the same. A more common practice would be to set both of their weights at 1, because they are of equal value and they are not being added together.
2 - As far as I know, the "grade to pass" option is only a cosmetic feature. It color codes grades in the grader report... items below the passing grade are colored red, and at or above are colored green.