The CYA test in the K2006 is pretty bomb-proof. The CYA tests on strips are notoriously unreliable.

You'll need to adjust your PM doses upward to levels that leave you with at least 5 ppm in the early AM, after working overnight, in order to make headway with the algae.

Also, if you can buy some dichlor, and use it to maintain some chlorine during the day, you'll be raising your CYA at the same time. With a 40K gallon pool, you might want to look at a 50# container of dichlor from Sam's. Here locally, they are $110, which is cheaper than I can buy it wholesale. But do NOT buy the mixed or blended shocks!

If you do get some, you might want to do something like broadcast 5# of dichlor (about 10 ppm FC on your pool), brush your walls, and then add 12 gallons of bleach just before dark.