Re: How much baking soda?
Wtih your stabilizer that high the adjusted TA might be a more valid reading. CYA will test as part of the TA. When the CYA is in normal ranges it can pretty much be ignored but when it is as high as yours it shows as a large chunk of your TA. My advice would be to do a partial drain and refill and get your CYA down to about 30-50 ppm and then rebalance the water.
11.75'x23.75' kidney 6.5K gal IG fiberglass pool/300 gal acrylic spillover spa combo; Aqualogic automation/SWCG; Pentair Clean and Clear 150 cart filter; 1.5 hp uprated 2 spd Pentair Whisperflo pump; PF:17
Retired pool store and commercial pool maintenance guy.