Right, but your sugar measurement itself would also be off from all the alcohol screwing with the density on the hydrometer.. Unless, you have some really cool toys that measure the sugar content independent of density. Not that I criticizing your method at all of measuring your sugar just wondering what ABV that measurement was taken at was all.....
I bet you it would be possible to construct a correction equation for the sugar concentration brix (gram sugar/gram wine+gram sugar) in wine with varying ABV.. Would not be very hard to do it either..... that way we could get a "proper" brix measurement no matter how much alcohol was in the wine.
Yeah, once you fortify it up the yeast is pretty much down and out for the count. Do you have experience with using Hungarian oak?