@WizardofCoz, thanks for all the details. I would agree with the checks that @ixu is suggesting. It does look like you have installed correctly as long as there aren’t any other taps or splits between the revenue meter and those mains in the top of the breaker box.
The other thing I would do in your shoes is try the export function which seems to be available to you. You might discover that it outputs the real accurate hourly (or even 15min) usage values, instead of the rounded values. If it does, I would do a Sense vs. utility scatter plot for hourly usage. If your utility does round the hourly data in export (and that rounding is annoying !), then I would do a daily Sense vs. utility scatter plot with the general methodology here.