With zero CYA, your chlorine shouldn't last more than a couple of days, and won't even last one day without a drastic reduction.....so I would consider taking a sample of water to the pool store, or better yet, buy yourself a good drop-based test kit and test it. Even so, with zero CYA, a Cl of 10 is pretty high, and I don't think I'd swim in it until it comes down to below 5.

The more important problem is the pH, though--keep at it with the borax, and aerate the water if you have a way to do so.

Janet