If there is one thing I have learned is to be patient with the pool chemistry. When I was a young impatient pool owner I would dump all my chems in at once and expect it to be ready in an hour. I started to realize this was more like college chem class, and not like adding creamer to a cup of coffee where its ready to go in two stirs of the spoon (he says as he sips on his cup of morning joe). CYA takes time to dissolve and to start binding with the CL. It probably approaches the target asymptotically. And if you add too much your only recourse is to drain and refill (like with Salt too).. and that just screws up your other numbers as well. SO I tend to add all my chemicals in a incremental fashion. If my calcs say 20#s of yadda yadda, I add 10 and test. Then I add 5 more and test, so I creep up on the target. Sometimes I would stop short of the target because it affected another value, but I am in the range I needed. The pool chem area list chemical properties that change in reaction to there other chems. I made a little reference card of those relations and stuck them in my test kit.
Sounds like you are on your way!
My hope is that by end of this week I will have an empty sock and be able to test CYA levels.
I agree 100% with you on adding a little at a time and testing... in the case of my CYA, the numbers needed to go up so much that I figured I would be fine doing about 2/3 of what the calcs said and going from there. I am taking that approach mostly because the kit I bought looks like it only has enough to do the testing 5 more times and once I get things on order I can see myself testing this monthly so I imagine I am going to have to start looking into replacement Chemicals for the kit soon.