I have recently started brewing with R/O water using the same spreadsheet. I second not adding any baking soda. I add small amounts of Epsom salts like you have listed and similar amounts of Gypsum and CaCl2. If I need to bring my PH down I add acidulated malt to to the mash. So far my beers have come out very good but I still need to get a Ph meter to make sure things are truly in line.
My rule of life prescribed as an absolutely sacred rite smoking cigars and also the drinking of alcohol before, after and if need be during all meals and in the intervals between them. - Winston Churchill