[Ryuji]

I'm not sure if you wasted your time or not. It was at least for your learning experience, although I could tell you just the same thing if we got to talk before :-)

If your formula makes any different result from standard D-76, it must be due to difference in pH and different sulfite concentration.

Firstly, I don't see any reason why Crawley said metaborate worked better than borax. He might have just meant higher pH. If the pH is adjusted to the same point by NaOH, both borax and metaborate make chemically identical solution. Don't believe the word "highly buffered" etc. alone, as they are relative terms.