Hi Kevin. Jan is giving you excellent advice. Another way to estimate how much bleach to use is that with 0 FC, you'll need 8 1/3 gallons as each gallon (they don't sell it in gallons anymore, do they?) will add 3ppm of FC.

Or you can use 12.5% liquid chlorine. If the per gallon price is less than double the per gallon price of 6% bleach, it's a good price, because you use half as much.

Having been in your situation (at least the low pH part) in a 20K pool, same size, I would be a little more aggressive than Jan with the first dose of Borax and use a whole box. It may be less than 6.8, but at 6.8, in 20k gallons, 1 box of Borax won't overshoot your ideal pH target. Again, I've been there a couple of times and it will EASILY take one box. The second box, if needed, go "halfsies".

Carl