I am a new pool owner and have read many posts here. I now have a question.
22000 gal in ground, wet edge pebble sheen finish, Clean clear 420 cartridge filter 10 ft spa. on well water Flagstone coping

FC 2.0
tc 2.0
CH 150
CYA 60
TA 110
pH 8.0
tds 1000

well water tests 800 tds

startup 1 month ago 2 weeks in filter has tan buildup and pressure is 30. Cleaned filter and PB said he notices scale on the bottom of the pool and I should add metal free and jacks magic purple stuff to fix scale. I have been fighting the pH all along.
Now RB wants me to add 20 gallons of muratic acid to shut down pool and clear out the scale. the scale looks like to me about 1 foot in diameter in 3 places.

I am more than concerned about this acid bath.

When I had the water tested they suggested to get the CH up first then add another chemical to handle the scale problem.
I am also seeing sand appear and am guessing it is from the flagstone.
Any suggestions would be appreciated.
Thank you