I have a symfony2 frontend application and I'd like to delegate all the asynchronous comunication with facebook through a node.js wrapper API, so if facebook change things I have to work on the nodejs API only. Is it possible? Can I let the user authorize the app and grant permissions starting from the frontend app and then let the node.js app wrap all the communications with the facebook API for the frontend app?
Yes, that is possible. You just pass the access token you obtain for each Facebook user to the node.js wrapper API.