Hi, and glad to see you're still around too!!
Answering last question first, I strongly suspect you're fighting an algae bloom--that CYA is awfully high, to the point where Cl of 8-10 should be your minimum. I strongly encourage you to drain about 1/2 your water and replace it, if it's feasible for you, because you're gonna have a hard time keeping it clear if you don't. After you refill it, shock it to 25 and you should see it clear up.
With the CYA that high, I'm not surprised that your pH is that low, either--remember, most pH test blocks only test as low as 6.8, so in reality it could have been much, much lower, and trichlor is a huge culprit with low pH. Keep adding Borax and testing, but you need to get that pH up into the 7.2-7.6 range as soon as possible. You don't mention a level for TA, but if it's high, then the pH is going to be more resistent to moving, which may explain why it's taking so much Borax to raise it.
No matter, the important point is that you raise the pH as soon as possible......I don't know what your fill water pH is, but if you're going to drain/refill for CYA, then refilling the pool will help raise the pH too, since tap pH should be higher than 6.8.
Janet
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