I spoke with Tom Mitchell, the owner of Fall Bright vineyard, where I purchased the Riesling juice. Turns out that Tom purchased a portion of the 2008 Riesling grapes from another vineyard in the area, which he said was not his usual practice (now he tells me). He said that others who purchased the Riesling had experienced similar issues with acid, but mostly found the color to be too dark for their taste. He said he was conducting test to see about acheiving the proper color.
I gave Tom an explanation of my starting and ending TA and pH numbers and the steps I had taken thus far. His recommendation was unique. He explained that I was likely not getting enough of a reduction from my cold stabilization because the pH was too high. He recommended lowering the pH to 3.2 by actually adding more tartaric acid to the wine. He said that when I place the carboy back in freezing conditions for one week, the acid will drop. I will give it a try. Since it is too late in the season to stabilize in the garage, I will need to use the refrigerator as a wine freezer.