Battery Life Estimation - Sanity check
"... So total period is 607 seconds, meaning ~0.012% of the time unit is drawing 5mA ...*"


No, it's 0.012 of the time (with no '%' symbol). That's 0.012/1, not 0.012/100 of the time.

That means that the remaining time is 0.988, not 99.988.

$$ 0.012 \times 5 + 99.988 \times 0.07 = ~7.0 \ \text {mA} $$

should have been 

$$ 0.012 \times 5 + 0.988 \times 0.07 = ~0.127 \ \text {mA} $$