As mentioned, chalk is not very useful for brewing use since it takes extraordinary measures to get it to dissolve fully. Pickling lime and baking soda are more effective at adding alkalinity to mashing water.
One thing that alarms me with the OPs post is that it shows them adding alkalinity-increasing minerals to the mashing AND sparging water. I'm hoping that this was just an oversight by the OP. Sparging water should always have low or no alkalinity. If BS3 is making that recommendation, then shame on them for reducing the quality of subsequent beers for their users.
While some think that a big malty Porter needs a lot of chloride in the water, its not necessarily true. The OPs original water quality is pretty high in chloride and could end up with minerally tasting beer. That's OK if that's your goal. An important take-away from this discussion is that an extra malty chloride/sulfate ratio does not make your resulting beer maltier. Malt and the lack of bittering are what make beer malty. That is the reason why you no longer see me using terms like Malty or Bitter for the chloride/sulfate ratio. Those terms are FALSE. Substituting the terms Full and Dry are more descriptive of the effects of chloride and sulfate.
If I were making this B Porter, I wouldn't go above 150 ppm chloride. The other concentrations are OK. The 50 plus ppm sulfate is OK too. Sulfate could actually be higher since having a somewhat drying finish in a big malty beer is actually helpful for the overall perception. To illustrate this, brewers should understand that Russian Imperial Stouts were largely brewed in Burton with their high sulfate content water. They were big and malty, but finished dry. That invites the drinker to take another sip.