Okay, thanks.

The stabilizer you added via the skimmer is going to get hung up in the sand filter until it has dissolved. This may take a day or two, depending on the stabilizer. The flaked product seems to dissolve quicker than granular stabilizer.

Do not backwash for a while or you'll just wash it all out of the sand.

Have you given some thought to buying a FAS-DPD test kit so you can do your own testing and don't have to rely on the pool store? Pool stores aren't always entirely reliable with their water testing.

How does your water look today? Still cloudy?

I'm signing off for the day, I'll check back in tomorrow.