This is incredible information. I'm amazed at how much you have found and can't thank you enough. "William J.", Horn might be the match. (One that was showing William David on one of my searches? I've not been able to find it again, but it was showing up as locked on ancestry.com or something like that when I did some searches for Virginia Adeline Hoyl. As I pulled on the thread I found him listed as spouse, and another listing of a death of the same name in 1862 in Dade county. I could not access any of the details.)
Since the Horns, Hoyls, and Hoovers appear to have been Unionists or of German/Dutch type ancestry as best I can tell, it follows that the best explanation is that Virginia's first husband was a Horn hung by Confederate guerrillas--rather than Yankee soldiers as my grandmother recalled the story. Either that or there is an even more convoluted and lost story about why he was hung by Union men, yet she married a Union soldier during the war.
I had started out operating on the assumption that I would turn up a direct Confederate line in this search and that it was set in Virginia, but it appears that was all incorrect.