You've put awesome amount of work into this!

As for RAC formula, as I have already explained under Hive account@jefpatat ' s article,

Instead of an overcomplicated form:

decay = exp( (-t/7) x ln(2) )

you can use:

decay = (1/2)^(t/7)

as:

exp( (-t/th) x ln(2) ) = e^( (-t/th) x ln(2) ) = e^( ln(2^(-t/th)) ) = 2^(-t/th) = (1/2)^(t/th)

For some reason this non-simplified form of equation is copied all over Internet. Maybe because it looks more 'scientific' with exponents and logarithms than simple 1/2 to power t/th? The latter one is easier to understand and you can easy see that if t = 7 days RAC =1/2 or is halved.