If Tesla is not blameless, then it is not driver's fault 100%. Total blame cannot exceed 100%.
[1] https://pro.bloomberglaw.com/insights/litigation/contributor...
https://en.wikipedia.org/wiki/Joint_and_several_liability
If we're talking about tort law, then yes, damages are measured in dollars. And those damages are absolutely subject to rules about how they are split when multiple people are liable.
If we're talking about crimes, then "percent of blame" is nonsensical. There is no percent liability for a crime, you either are guilty or you are not.
This situation is the opposite of that, because multiple people were knowingly reckless.
Edit: By "multiple people" I mean the driver and Elon.