Instead of assigning 1 point (or more) to a question, the points should be assigned to the answer chosen. This way, a semi-correct answer may be given a 1-point reward, whereas a fully correct answer would be given, say, a 3-point reward. Making negative points a possibility, you may also reduce the subtotal if the respondent has checked too many options.

And: GET RID of the parenthesis saying how many points each question will give. On questions with multiple more-or-less correct answers, the parenthesis reveals how many options one should check