Not sure about pool proof probably expensive borates, most on this site either use 20 mule team borax or order in bulk if you do go the bulk route granules are preferred as the powder tends to fly around and cause a mess. A pool your size will need 1300 oz. or 81 LB to get to 50ppm, you want to target 30–50 ppm. Amazon sells a 6 pack or 390 oz. total of 20 mule for $39.21.
Most of the threads I read around water feel or skin issues usually recommend salt. I have no idea if it is because salt is better when it comes to feel or if it is just that it’s less expensive and easer to deal with I suspect it’s a bit of both. You can do both in fact even if you don’t actively add salt over time you will build up some in the water from MA and chlorine.
I added borates a couple of months ago and the water defiantly feels better and as many have commented it sparkles. We swam the day after it was added but that was mainly due to it being the end of the day when I added. Once it is all dissolved and your pH is back in range you can jump in, I would say a couple of hours with the pump running to be safe.
I would recommend borates, we like the look, feel, stable pH, and it seems to have reduced the back swimmers we get in the pool before we added there would be 5 or 6 of them in the pool at any one time now I see one once in a while.