Fry was probably as good as it gets for the time. I am fairly sure the River named Konhaway was the Kanawha, phonetically correct just a different spelling? The map seems to make more since that way although it is still littered with mistakes. New River area seems wrong for instance. As with most cartographers of that time, they don't navigate all the waterways, they assemble information from various sources and piece it together. Since in the 1750s there were not a whole lot of people settling West of the treaty boundary (Lord Halifax Line on map) it is bound to have mistakes. I think Gist did his exploration around this same time 1750ish? Pay attention to the Western edge of the map and the Guyandotte River and the Louisa River flowing into the Cole. I don't think the map goes far enough West to cover the Sandy.
https://en.wikipedia.org/wiki/Kanawha_River