Having worn the vigneron boots in Malibu for about nine (attempted) harvests, I know exactly what you're going through. I tried biodynamic practices and the vines grew quite well, but the grapes weren't so good. Then I added more protection for the fruit while maintaining the vines and the birds got them. This went on for years, with nothing going quite right. The fact that our vineyard was about the only fruit source for the local mammal population within a couple of miles didn't help, and the morning fog and afternoon heat provided some fine lab-level environments for all manner of mold and insect pests.
Part of this may be due to there having been only 150 vines on the property. A larger site/denser planting might have resulted in a higher rate of success (which is perhaps redundant, given that anything more than 0% is a "higher rate"). Adding insult to injury, the people who bought the house when we moved to Dallas were not wine drinkers and didn't maintain it as a vineyard. They might as well have put up a sign along the lines of "Deer Eat Free!!"
It provided good exercise, some intense education on farming in general and viticulture in particular, and I met some interesting people in the process.
-Eden (when I think about how much money I pumped into the vineyard, I probably could have been buying 1er and Grand Cru Burgundy for the same amount)(maybe even Napa Cabernet too!)
Your intrepid vigneron-in-training,