I have taken care of my pool for 21 years and have seemed to run into a snag that I never have had before.
I test with Taylor kit 2006 and these are my current readings:

PH 7.4
TA 180
FC 25.5 yes this is true I supershocked last night with calcium hypochlorite
CC 1.0 only budged .5 after following calculator recommendations.
CYA 180
CH 130

I have a 16x32 inground vinyl pool. I have been unable to get my chlorine levels down in over a month and realize that this is due to the CYA levels from having used Trichlor tablet over the years. Last year I switched to the BBB method but would occasionally put a puck in the skimmer to keep chlorine levels up as I have many kids coming in and out of the pool. We fill with well water and I tested the water yesterday and found the TA levels to be 320 which explains my increased levels. I have been slowly bringing it down with Muriatic acid but don't seem to be making much headway as I get it down and then need to add water due to loss. We have a building over the pool so not much chlorine is loss due to sunlight.
I am just wondering if I need to dump some water again and add new but then worry about the TA levels going back up. In looking at the CYA/Chlorine chart I see my numbers are not terribly out of whack but I don't want to increase the chlorine in fear of getting too high. I usually shock with bleach but am using the hypochlorite to avoid adding to the FC number. Am I wrong in this? Any help would be appreciated as I have never had this kind of problem in 21 years.