I assume that this is bottled spring water, correct?
Why are you planning to dilute with distilled water. None of the mineral levels are a concern, especially for a darker and more strongly flavored beer.
Given that you are looking for a more malt forward beer, I would swap the amounts for Gypsum and Calcium Chloride.
The need for the baking soda is difficult to tell. What color are you shooting for? And how much of this color do you think comes from roasted malts (25, 50 or 75%)?