That is indeed a substantial amount of exercise! Awesome work.

In a thought experiment (where it's possible to know the exact amounts) -- do you think consuming exactly 2k kcal is perfectly even with burning exactly 2k kcal? IE, is there overhead to transform the energy? Does it account for physical/energy waste?

I don't know, anecdotally it seems that if I spent X calories exercising, my hunger will adjust until I consume roughly X extra calories.

The energy expenditure does account for waste, I think only about 20-25% of the energy spent is turned into mechanical output

2000? The standard estimate of net calories burned (cals above basal rate) is 0.98kgkm (i think it is 0.98, i usually round up to 1).

You might enjoy this: http://theoatmeal.com/comics/running

That should read 0.98 × kg × km

0.98 x 73 x 25.75 = 1842 kcal, not too far off

I have experienced the same issue when I burn larger amounts of calories. I've found burning about 500-800 calories (I run for about an hour) at the end of the day some time after dinner is my sweet spot.