Well the recipe Ive been using is VERY simple ha ha
--6 bottles of Welch's black cherry Concord grape juice
--Lavins D47
--2lbs turbinado cane sugar
--two tsp grape tannin
the final product after two weeks of fermenting has a very smooth and full bodied flavor, however if it is not sweetened it has a crisp bite to it which people who have tasted it describe as bitter..... after I sweetened it with a further pound of turbinado cane sugar there was a good balance of sweetness and bitterness. For the batches that I do not sweeten I may try using calcium bicarbonate as you mentioned and potentially less tannins.
The recipe itself is great and unlike most wines Ive tasted but it will go down smooth and still put you on your ass after a couple glasses haha cheap and simple