Glad we can help. As for your CYA, you have the right idea - exchange water. As we approach the cooler season, you have to ask yourself if you want to do a partial drain now and adjust chemicals from there, or simply try to maintain a higher FC level somewhat commensurate with that high CYA to keep algae away. Once your water temp drops, you should be okay. You may get some rains over the winter that help to replace/exchange the water in there now which will help to lower the CYA a bit. If you're curious about how high your CYA really is, you can try the CYA Dilution Testing as follows:
Add pool water to bottom of sticker.
Add tap water to top of sticker.
Shake.
Pour out half so mixture is to bottom of sticker.
Add reagent to top of sticker.
Shake.
Test outside with back to sun and tube at waist level.
Pour back and forth a few times to see if you get the same result.
Double the result.
It's not perfect, but it does give you a better idea how much over 100 you may be.