I would say, there is no specific forum that is strictly dedicated to Facebook questions. However there are like two other forums that i know apart from Sitepoint where you'd get instant replies on almost about anything you post. There is Bloggeries and Digital point. For your case, Digital point will meet your specifications( facebook) since it has a dedicated section for social media where topics on facebook, google +, twitter etc. can be discussed. Again its very general.
Hope i have answered you well.