Many if not most tanks can handle saturated limewater for all evaporation replacement. If not (meaning pH or alk get too high) just add less solid lime to the limewater. 
do I need a powerhead in Kalk to keep it mixed up?
I currently use kalk with my ATO. It does not maintain Ca and alk where I want them so I started using two part dosing (recipe 1) from BRS. My question is, would it be better to do two part only with RO/DI ATO, kalk only, or is it ok to continue as I am. Thanks