Is the Benjamin who died in 1799 the one buried at Dowland? He is described as aged 60 so born ca 1739. Banns were called in both Winkeligh & Iddesleigh. One of the witnesses was a Benjamin VANSTONE Senior - possibly his father?
There is also a will for a Benjamin VANSTONE dated 1785 and a burial at Dowland in 1785.
A Benjamin VANSTONE was baptising at Dowland 1743-1749, wife Mary. Unfortunately for you, Dowland registers only exist back to 1742. BTs do exist.