1. I think you are confusing marketing with design; when product labels say "designed for X" it almost always means "designed to sell TO people with X", and not "designed by a team of engineers for optimal performance when X is present". I'm smirking, as I type this, but I'm perfectly serious in making the assertion.

2. I doubt anyone has actually studied the effect of different concentrations of HEDP in salt water pools.

3. I think 3 cups of the Kem-Tek product would perform identically to 1 cup of the Pink Stuff or 3 cups of the Purple or Blue Stuff.