The vinegar - apple cider vinegar - actually draws the minerals out from the bones into the stock. That's why you should leave it stand for about an hour before heating, not to destroy the ACV. An acidic wine will also do that, and perhaps lemon juice would do the same, not sure, sounds reasonable.
I read you ordered Price's book, look forward to you report. I wasn't sure if it would be too dry a read, so didn't get it. But a lot of the information is referenced in the Nourishing Traditions book - along with recipes and a whole section on organ meats (as I see you mentioned above).