As far as shocking goes, there is no need to shock weekly just on principle--you need to shock the water if 1) it's cloudy, 2) you have a CC of more than 0.5, or 3)you start seeing indications of impending algae bloom. There are some people who never shock the pools except when getting ready for closing--and then there are those who shock more frequently "just because".

It doesn't surprise me that your CYA is that high, if tabs are all the previous owners used with this pool. It doesn't matter that the water is "old", but lowering that CYA will definitely make the pool easier to manage! Can you imagine what nightmares the previous owners had trying to get/keep it clear?

Janet