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When raising PH from very very low values it is generally best to use borax, however you can use soda ash if you need to. Either way the TA is likely to come out a little higher than we recommend. Measure TA after the PH is where you want it to be and adjust if needed.
TDS is not an interesting number. It is best to completely ignore TDS, and concentrate on the numbers that matter, like the CH and CYA levels.
Very low PH will cause calcium to be etched off of plaster surfaces and go into the water, raising the CH level in the water. You need to be careful when doing a no drain acid wash to be sure CH doesn't end up too high, or you can have calcium scaling when you raise the PH/TA back up. In situations where you need to remove a lot of calcium, you may need to do water replacement to get CH levels down before raising PH all the way back up, but do raise PH at least part way to stop the acid wash before replacing water.