like the lady said, don't put vinegar in your ferment. leave the acidity production up to the bacteria.
when fermentation's done, you can further process it if you like (e.g. adding vinegar to taste).
i struggled with salt as well, and i'm not sure that everyone's on the same page.
read this and the following few posts:
http://thehotpepper.com/topic/23146-fermenting-peppers-101/?p=1566458
basically, there are potentially three ways to express salt concentration in recipes, and sometimes people aren't clear about which way they mean when they give general guidelines.
the first way is expressing it as a % of the brine e.g. 3% salt brine could mean 3g salt added to 97g total liquids used in the fermentation (yielding 100g brine).
this is problematic because if you're trying to compare with someone else's recipe, it only really works if you both have the same ratio of 'dry' ingredients to brine.
note that this figure is probably the most important one for food safety. i don't know exactly what it should be, but to inhibit unwanted organisms, the brine probably shouldn't be below about 3%.
another way is expressing it as a % of the 'dry' mash ingredients e.g. 3% salt could mean 3g salt added to a fermentation containing 100g pepper.
the third (and imo best) way is expressing it as % of net weight e.g. 3% salt could mean 3g salt added to 50g pepper + 47g water (yielding 100g total).
i think this is overall the most useful figure because it gives you the best idea of how salty the ferment will taste in the end. but you still have to make sure your (initial) brine is salty enough to inhibit unwanted organisms, so calculate that too.
note that in this example, the initial brine concentration is 3g salt / 47g water = 6.4%, but it would decrease over time as it approaches equilibrium and salt diffuses into the veggies.
