Hi and welcome to the Pool Forum!

A dose of about 1/4 of a cup should be about right. If you don't have dichlor yet, you can just use bleach until you get some. The directions are in the 'recipe.'

If you have trichlor tabs in a floater, that is most likely the cause for your low pH as they are very acidic. The Borax doses will raise that up.

You might want to see if Walmart has an HTH 6-Way drops-based kit (not test strips). That will allow you to measure more than just chlorine and pH. You'll want to know what your CYA level is after you have been using the dichlor for about a week. A CYA level of about 50 is good for most pools. At that point, you'll want to switch to just using bleach.

It is really important that you maintain good chlorine levels. These little pools are actually harder to deal with than bigger ones because they have such poor filtration that cleaning up algae can be a nightmare. So, be diligent and keep it algae free.

Hope this helps. Come back if you have further questions.