It's a good sign that the TA is now up which means your pH is definitely above 4.5 at this point. If the pH still reads 6.8 (so it can be below that) then if your TA is already high enough you can just aerate the water and that should get your pH up. In fact, if your TA is getting close to 80 ppm you should find the pH getting above 6.8.
Since your CYA is low (around 20 ppm) you don't need to add very much chlorine and you should get your CYA level higher if your pool is exposed to sunlight. You can add both chlorine and CYA by using Dichlor or you can add them separately by using pure CYA (that dissolves slowly -- see the Pool School for adding it to a sock over a return flow) and chlorinating liquid or bleach.
Since your CYA is low (around 20 ppm) you don't need to add very much chlorine and you should get your CYA level higher if your pool is exposed to sunlight. You can add both chlorine and CYA by using Dichlor or you can add them separately by using pure CYA (that dissolves slowly -- see the Pool School for adding it to a sock over a return flow) and chlorinating liquid or bleach.