Mike,

I'm not sure why you are going through all of these calculations. If you
set the regeneration time too long you will quickly realize that there is a
problem and do a "manual regeneration" thus throwing all of your
calculations out the window. Your water supply apparently has a variable
hardness so set the regeneration time assuming the highest hardness and your
water will always be soft. If you try to be super efficient about
regenerating you will certainly fail because the actual water hardness
varies. Set it and forget it.
I'm pretty sure that you need a "fudge" factor when you substitute KCl
for NaCl.

Dave M.