For future use in your water profile, I would ditch the chalk and use pickling lime instead. Chalk is notoriously difficult to dissolve in water, it has to be really hot to force it to go into solution. Pickling lime dissolves pretty easily and works the same way as chalk in the mash. You can find it in stores that sell food canning supplies.
For a Pils you want really soft water. I ran the water profile for Pilsen water through Bru'n Water and if you leave out the chalk or (pickling lime) you will be fine. The rest of the minerals are pretty much on the money for a Pilsen water profile I assumed 3.5 gallons of water for your mash which is 1.3 quarts/lb. I normally go 1.5 quarts/lb (4 gallons) but your brew system may have volume limits You can go with this or use Brewbama's idea. The predicted mash pH at 3.5 gallons of mash liquor was 5.69 according to Bru'n Water so as Denny and Brewbama mentioned, a bit of lactic acid or a small amount of acidified malt will help bring the pH to the proper range.
Personally, I don't put water salts in my sparge liquor, I just acidify the distilled water (in my case Reverse Osmosis water, which is the same thing) with phosphoric acid to get the pH in the 5.2-5.6 pH range. That said, adding minerals to the sparge liquor is your choice. If you don't have a pH meter, you will probably be OK sparging with just plain distilled water as the mash will act as a buffer to keep the pH from getting too high. If you don't already have one, you should consider investing in a pH meter and calibration solutions. It is a valuable brewery tool.
Regarding doing a decoction, I personally wouldn't do one for this beer but again that is your choice if you want to play with learning how to do decoctions. The malts today are really well modified and you really don't need to do one. A single infusion mash at 152 would be fine, but it's your beer so you can make it like you want.
Just my .02. I am sure others will add to this as well.