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?
Sorry for the lack of a reply. I know imgur hosts only images lol, I'd probably have to use one service for images and another for videos. And yeah it'd have to use some kind of token or authentication and the host would have to allow private content. Guessing that doesn't exist, but just wanted to check.