I used to be blind but now I see!
I received my TF-100 Test kit last week and began doing my own testing with my new Speed Stir. What I found was that the pool stores are worse than I thought. I began paying close attention to how they run the tests on the day I ordered my kit. I noticed that they use the most basic tests for chlorine and for CYA. What I found was that they were dead wrong most of the time.
I took water samples to two different pool stores within minutes of each other (both samples were taken from the pool at the same time). You can see how wide they vary. They both wanted to sell me chemicals. One wanted to sell me a big bottle of Copper Algaecide!
Here are my test numbers after getting my TF-100 test kit: