I was born and raised in Charlottesville. Pretty much know my way around the Albemarle, Louisa, Fluvanna and Augusta County areas.
As to deeds. I suspect magnetic variation plays a large part in varying line directions and yes dragging chains through woods and meandering streams, rivers and creeks plays a part as well. 5 degrees and 10 to 15 poles is not a lot considering what they were working with and the fact that the land may have been modified since the last survey.
Just curious, but how are you doing these surveys without the aid of a computer? Seems you will require a very large piece of paper to complete your work. What area are you starting with and what time frame?