The last time that I added calcium hydroxide I was trying to match "Black Full" profile in Bru'nWater for a Russian Imperial Stout:
* starting with soft water with 3 ppm sulfate and 4 ppm chloride and 5 ppm calcium
* campden to neutralize chloramine -> 20 ppm sulfate
* added enough Epsom salt to get 5 ppm magnesium -> 20 ppm sulfate
That was as much sulfate as I wanted (total of 44 ppm), but Calcium was still only 5 ppm
* Calcium chloride to bring chloride to 42 ppm, which only brings calcium to 27 ppm
I still need ~25 ppm calcium
* Pickling lime to bring calcium to 55 ppm
Because this was a very dark beer with a lot of roasted grains I didn't need to add any acid to counter the pickling lime. I got pH=5.45 with no acid addition.
this is one of the things I think Bru'n water makes needlessly complicated, they have magnesium, sodium and bicarb levels for brewing profiles. When you start out with RO, or in your case fantastically soft water, just add Calcium Chloride and Calcium sulfate to get your chloride and sulfate levels in range, and then either use an acid or base to get your mash ph in range. thats it. Dont fret about the other stuff.