Lynn,
Without performing Paper Chromotography you cannot determine which acid is dominate. And even with that, PC does not give you %, because it is only a qualitative. In most, if not all, cases your wine will contain a mixture of Malic, Latic, Tartaric and possibly Citric. In many test kits that refer to the acids in PPT (parts per thousand) it is "expressed" as sulfuric. You are correct in that the wine does not contain sulfuric. What I mean by expressed is that when a titration is performed, there is a calculation that takes the amount of NaOH (base) used to nuetralize the acid and convert that, by calculation to be expressed as a particular acid. An example would be, if you did a titration and converted the acid to % latic and then calculated it and expressed it as % Sulfuric, the latic value would be a much higher % because it is a much weaker acid. In other words, it takes much less NaOH to nuetralize 1% latic than it would to nuetralize 1% sulfuric or tartaric.
Now, with this said, it really doesn't matter how you express it, just that you do it the same way all the time. In most cases the standard for most test kits is % tartaric. This is what i use and it works well for me.
I hope this has helped.
Hal