It'll be interesting to see the result of your metals test--if you do have a high metal content you can use sequestrant.....take a look at Marie's (mbar) posts in the metals forum--she's the resident expert and has given lots of good information when it comes to dealing with metals. Is your fill source from the municipal water supply, or is it from a well?

I believe soda ash also raises TA along with pH, which may be why you're not getting as much rise in pH as you expect, but I really think your pH was much, much lower than you originally thought, which explains the huge amount of Borax being used to get it back up to normal ranges.

Janet