Too much is really relative to the overall acid/base of the diet. I think if you get any type of mouth sore You have teken in too much, but that is just a guess. You can use the values from Loren Cordains site to calculate the NRAL of say a tablespoon of vinegar to see what it it doing to your overall intake.
I'm doubtfull of the cider vinegar mineral content, but hav efound nothing conclusive one way or another. Perhaps the merck manual or the USDA food database?