Max HR you can sort of estimate through max efforts as you've done, but VO2 requires lab testing and they'll get your max HR at the same time. I'm getting ready to do it and it will cost around $100 here.
As far as I know, the Polar uses averages for weight and sex to determine calories. I've used an HRM as a calorie counter effectively to lose 60 lbs. so I have to assume it's pretty close to actual consumption.