Tracking completion in a branched scenario course

Hi awesome Articulate community.  I need your help.

I have a course that contains branched scenarios.  The learner can complete the course without touching every screen, which is fine but leads to the problem -- How do I track their completion?

From my understanding, I need to either set the tracking to 1) Number of slides viewed, or 2) Track using Quiz results.  

My issue -- when I set it to the lowest # of slides, people can earn a completion too early.

When I set it to Track using Quiz, it doesn't mark as complete. I have a quiz within the course where the learner must try again until they get each question correct (earning 100%).  My LMS is terrible, so I need to make this dummy-proof.

My wish:  That I could set Variable that is triggered on the last slide that says all slides were viewed (= completion). 

Thank you!