Why are my calculations for O2 requirements of daily metabolism so far off?
The math was correct, but there was a misunderstanding in what some of the numbers represent. The energy expenditures listed for RMR include resting dietary thermogenesis in addition to the actual ATP energy used for work. You can see that the same is done for reporting Calories in food (e.g. 4 per carb) at http://www.fao.org/docrep/006/Y5022E/y5022e04.htm

When this is taken into account, we use 686 kcal/mole of glucose to get similar oxygen numbers. This includes the energy for the ATP and the energy from heat.