I'm tagging along. I have posed a portion of the question to a friend from college, who is a chemistry professor now.
Last thread someone suggested 1 gram CaCl2 and 0.5 grams Ca(OH)2 (aka slaked lime or cal). I am not entirely sure these two will dissolve together or not, as the lime is poorly soluable in water, though I think that you need to know what the cacl2 is doing to the pH and what the isoelectric points are for the lime.
If you're starting with RO or distilled water ph7 so that's right on target. But not sure how the two suggested additions will buffer each other. Seems the CaCl will act as an acid and the lime as an base, and should be getting the hardness from the ca and the bicarbonate for the OH groups. I am way over my head anymore on the water chemistry stuff though.
I think you need to calculate the mol's per gram of each constituent to get your ppm values. A little Wikipedia search on avagadros number might get you started if you want to calculate yourself.
I am hoping my chemistry professor friend or maybe a forum member chemist can chime in.
Edit- he said the effort benefit ratio was way out of whack and suspects solubility problems...