Hey, not sure if anyone is still looking at this, but if so a couple of things:
1. NEVER EVER use chemically ionized softened water to brew with. The idea in this is that Ca2+ (and to a lesser degree Mg2+) is replaced with Na+, or sodium, at a level that is unsuitable for brewing. under 150ppm or so is ok, but this will be way over that. You shouldn't even drink this water on a normal basis, and it will ruin your mash profile.
2. Hardness and Alkalinity are important to the mash because of the enzymatic reactions that take place DURING THE MASH. by the time you boil, these reactions have or have not already taken place, so its not a factor. Take a pH reading of your water, take a pH reading of your MASH after it settles, and you'll notice that it has dropped significantly. The enzymes and processes of the Mash will buffer the wort to around 5.4 or so,+/- .2 If not, you have an alkalinity problem, and should either have it tested and add salts or acids as such, or add distilled water to your mash water to lower the overall alkalinity and hardness. The other option is to just buy water from the grocery store, always in a moderate range good for brewing. you can usually even get a water report on it fairly easily.
If you're really curious about this and don't want to spend the money on testing, you can always do small 1l batches of mash, adding a bit more distilled water each time to your strike water, and check the pH until you get into that golden range.
Also, just a note, if you have city water, not a well, make sure to use a carbon filter somewhere in the line if using for mash water, Chloride/chlorine will affect your mash negatively as well. also, do not use 100% distilled water to mash with either, the water must have trace amounts of ions in it for enzymatic actions and yeast nutrient. You can however make/buy distilled water and build your own water from scratch if you are trying to mimic a certain area, ie. Burton on Trent for ales or Munich for lagers.
Hope this helps.