var meta = module.parent.require('./meta');. Then, meta.config may have the configuration (might need to double-check that). var nconf = module.parent.require('nconf'); will allow you to hook into the configuration utility we use: nconf.get('url') returns the full url.
Unfortunately not -- our hooks are designed to keep the information passed in to a minimum.
The posts.parse hook is called whenever a piece of content needs to be "parsed like a post". It is not strictly a hook that is called whenever a topic is loaded. Perhaps you can look into filter:post.getPosts?
I just did an install of NodeBB 0.8.2 and it installed nodebb-plugin-emailer-mandrill 0.3.1 with it which is only compatible with NodeBB 0.9.^. In addition to the declared version problem I was also getting a socket.io/helpers related error on NodeBB startup until I removed the mandrill plugin.
I worked around this problem by removing mandrill and then installing it like this:
npm install email@example.com
I poked around to see how nodebb installs nodebb-plugin-emailer-mandrill and it appears that this plugin is installed in a special way? It is not mentioned in the package.json requirements for nodebb.