Yes, for *all* your makeup water (evaporation) use the mixed kalkwasser. Take the time to implement my method of using the 5 gallon bucket with power head. Complete detailed instruction are in the book.
1 Tablespoon per gallon (aprox)
You would use it as needed (how much water the tank evaporates) Kent is a well known brand and will definitely serve the purpose.
No, don't use that. That is Calcium Chloride, rather than calcium hydroxide (kalkwasser) Calcium chloride will quickly elevate the ph alkalinity but dosnt have long lasting effects. It will essentially *spike* the water chemistry. Kalkwasser will maintain and sustain calcium levels
Dont use that either ;-) Just use regular plain kalkwasser. Read the book carefully it explains all aspects of this subject.
420 is fine. don't get hung up in *exact* reading the tank will fluctuate just add regular kalkwasser and perform regular water changes.
Yes they have those stores here too, which prompted me to write the book. I strongly recommend to use the CD as described. There is a load of information on there. Good luck and please use the book. It will hopefully simplify your reefkeeping Best Regards Robert