Palmers numbers are a range to use to ballpark your water to and you can fall anywhere within the range. Palmer also has limits in the RA and hardness numbers. If you use his chart it can get to some pretty extreme numbers if you are brewing a very dark beer.
From Palmer he says when doing mineral additions do your first addition in the mash and base it on water volume in the mash. Do not add to the sparge. Do a second addition in the boil kettle and figure that based on the water above and beyond what was in the mash. So if you mash with 3 gallons base your mash addition on 3 gallons. then if you will boil 7 gallons, make a boil kettle addition based on the additional 4 gallons of water in the kettle.
The Brewing network has a 4 part series with Jamil and Palmer discussing water. It is a good listen and they cover some of the things you are asking about. Scroll down to find the water podcasts.
For alternative spreadsheets just browse the brew science forums. there are a couple members here that have set up their own sheets and some have some profiles included.
Primary: German Hef, Belgian IPA, Scottish 80, Belgian Dubbel
On Tap: Oatmeal Stout, Vanilla Oatmeal Stout, Belgian Dark Strong, Munich Dunkel, Dunkel Weizen, Oktoberfest, Bock, IPA, Black IPA, English IPA, Pale Ale
Using the mind to look for reality is delusion. Using your senses to look for reality is awareness.
"One time I was so desperate for a beer I snuck into the football stadium and ate the dirt under the bleachers." Homer Simpson
Life, Liberty, and the Pursuit of Hoppiness