The CYA test is intensive. I actually have a pint bottle of the reagent in a closet to refill the little bottles in the kits.

Unless your waterfall is a dribble, it will aerate your pool. Hate to say it, but the builder is probably wrong. Even pointing your returns at the surface aerates. On one of the few times I needed to lower TA, I used a cheap fountain sprayer the screws into the return. It was a lot of fun for the kids and worked very rapidly to raise pH.

As Watermom said, CC is a bell-weather. If you have a measurable level of Combined Chloramines, it means your chlorine is working to metabolize something, so you may have to shock your pool to get rid of that "something".