Well tonight I did a very smart thing: I took Pool Doc's advice.

I took apart my filter and checked the sand.
See where I'm pointing? That's all the sand left in the filter.
This explains a lot of last year's frustrations as well.
Honestly, it never occurred to me that I could be losing sand out of the backwash.

I do agree that the dichlor has gotten the CYA out of hand.
First things first: Purchasing silica sand from Concrete Industries tomorrow.