When you add a gallon in the morning, what is your chlorine reading in the evening? If it is all gone, then you need to add more in the morning and take it a little higher --- maybe 1-1/2 gallons which would take you up to 6. In the morning when you test, add enough bleach to get back up to 6ppm.

Give it 2 more days before adding more CYA. You are probably right that it should be dissolved by now, but you really don't want too much in there. So, if you go ahead now and add more and then a couple of days from now get a too high reading, you'll wish you didn't add more. So, give it just a little more time just to be safe. I have no idea what affect age has on CYA. ?????

For now, just work to maintain chlorine between 3-6 and pH between 7.2-7.8 and a couple of days from, get the CYA retested and post the reading and then we'll go from there.