Need Help with SL360 Freeform Assessments with Unconventional Scoring

Folks-

I'm working on a scenario-based assessment. Learners choose from one of three answers:

• Best - add 2 points
• Acceptable - add 1 point
• Unacceptable - subtract 1 point

I'm making question slides by taking my layout and using Insert Freeform Pick One. I'm tracking the score with a project variable, OverallScore. Each scenario has a maximum of three interactions/questions.

Here's how it works:

• Attempt 1:
  • If the learner selects Best, they get feedback saying they chose the best answer and why this is the best answer. On continue, add 2 to OverallScore.
  • If the learner selects either Acceptable or Unacceptable, they see feedback as to why it's acceptable or unacceptable and they can try again. No score update.
• Attempt 2:
  • If the learner selects Best, they get feedback noted above in Attempt 1 and we add 2 points to OverallScore on continue.
  • If the learner selects Acceptable or Unacceptable, they get the appropriate feedback and a See Best Answer button. When that button is selected, the OverallScore is updated (add 1 or subtract 1 as appropriate) and they see a This is the Best Answer layer. From here they select continue and move on.

I figured I just use a results slide to report results to the LMS since it would collate the three interaction/question slides. And the only reason I did the freeform thing is to have questions that I can assign to a results slide. But conventional pick one means there's only one correct and that's not the case here. So I thought I'd just update the Results.ScorePoints system variable with the value from my project OverallScore variable at the end. But you can't touch the Results.ScorePoints variable manually, at least as far as I can tell. 

Can I avoid using a results slide and instead have a summary slide with a submit results trigger on it? And will that just submit based on Results.ScorePoints? 

I really want to use the value of my OverallScore variable as the means of determining pass/not pass.

Suggestions are much appreciated.