I'm a serious Whitehall researcher that may be able to help.
First the Great Bridge is indeed in Virgina, just above the eastern border with North Carolina, it shows on some Va maps. The batte was very short although a massive battle that was the beginning of driving the British from Va. The North Carolina Milita came up to help in it. There are no official records that I have found that list the members of the NC Militia however, DAR recognizes Alexander Legrand Whitehall as a patriot.
These are indeed the Whitehalls that moved through Mercer County to the state of Washington, settling first in the area of Douglas County.
I can probably help you with filling in your blanks, however I need to have a little better idea of how you fit in. I only exchange information with bona fide family members who agree not to publish the data on the web or in other forms