The amount of driving 'necessary' for commuting is zero. You can live in a homeless camp next to your job, or the postage-stamp sized studio most people could afford within walking distance of where the jobs are. You may get hassled by police every once in awhile, but then again seems safer than driving. Perhaps roll yourself in bubble wrap as well and wear a helmet while walking there. I can name quite a few cities where you can wake up in a heroin daze and shit in the streets and be within walking distance of someplace to earn some cash.
Personally 99.9% of driving I do is for pleasure, the lever I have to adjust is miles I drive not the miles the average person drives. On an individual level, each person can directly move their "miles I drive" lever but only barely move the "average miles a person drives" lever. Deaths/capita is a societal measurement that only has limited usefulness to the individual human, who is determining his own behavior. Deaths/mile is more useful as it actually allows me to examine how dangerous the roads are and plan how far I want to commute or pleasure drive accordingly.
Deaths / capita also allows the twisted viewpoint that someone driving a million miles for pleasure gives a very wrong view to the person driving a few miles for necessity. You claim to care about the amount of driving 'necessary' but then use a figure that includes deaths from people driving to the cinema or bar or a road trip to Vegas, which are not necessary. If you only include deaths per capita based on 'necessary' driving it would be a hell of a lot smaller, especially in comparison to the change in deaths per mile.