Can't really help with the pH, other than to say, keep pH in line, and it'll all balance out.
Last year my TA was in the 140-160 range (due to the pool store guidance the year before) and pH constantly tried to climb to the stratosphere. This year, between natural drop and water replacement, my TA is at 100, and my pH has been rock solid between 7.3 and 7.5 with no chemical additions. My point is, just do whatever you have to in order to keep pH in line and see what happens. Your pool's "personality" will reveal itself.
As for the CYA, remember that it only leaves the pool during backwashing/draining or splashout. Water replacement due to evaporation won't change it. Here's an example....if your CYA is at 50, then water evaporates, the concentration might go up to say, 60. Then it rains (or you add water from the tap) to top it off, the CYA concentration will come right back to 50. Make sense?
EDIT: ARGH!!! Techguy beat me!