Ask Mr. Smarty Plants

Since you have already obviously done research on Ampelopsis arborea (Peppervine), we're not sure we can add anything useful. We did find an Aggie Horticulture article (Texas A&M) on Peppervine. We also discovered, in our Native Plant Database, another plant with the common name "pepper vine," Clematis ligusticifolia (Western white clematis). From our webpage on that plant, we extracted this paragraph:

"This species’ traditional name, Pepper Vine, referred to the acrid, peppery taste of the stems and leaves, which Native Americans chewed as a remedy for colds and sore throats. It is said that the crushed roots were placed in the nostrils of tired horses to revive them. Caution is advised: The genus is known to have poisonous species."

Since you are referring to a grape-like fruit, we hope this is not the right plant; common names can be easily tripped over in plants.

Everything we found concerning edibility said it was a food liked by birds, and mammals would eat it, but preferred other food if they could get it. We also learned that it can be very invasive and absolutely crowd out other more desirable plants in the garden or woodlands.

Since, as we said, we don't have much to add, we will voice an opinion. The process is obviously tedious to extract juice from those berries, and you mentioned stinging and burning while handling it. Are you sure you want that attacking the lining of your stomach? Oh, and were you aware that another common name of this vine is "cow-itch vine?"