How much dichlor did you add? Dichlor is fine to use for a short while. It has CYA in it along with chlorine. All pools need some CYA in them but too much will cause a problem. Can you see if your pool store does the disappearing black dot test to test for CYA. If so, let them test it every few days because you do not want your CYA to go over 40-50ppm. (If your Walmart sells an HTH 6-Way test kit (not test strips), it has the CYA test in it so you could do it yourself.

I think the reason you were having trouble keeping chlorine in the pool before was that you didn't have any CYA in there. CYA is kind of like sunscreen for your chlorine. Without some in the water, your chlorine is quickly lost to the sun.

Dichlor is very acidic and will drive your pH down as you have found. Your pool is really small so it is hard to recommend how much Borax to add so I'm going to suggest a little dose and then you can retest the pH after a few hours to see how much it raised it and then adjust and redose with more if needed. Maybe start with 1/8 of a cup? That's a guess on my part. Best I can do.

When reading your chlorine test, read it immediately. The initial color is the result.

By the way, no need to apologize for more questions. That is why we are here!