Well, the thing is, Node.JS is just executing JS code while providing some core modules. Nothing more, nothing less. If you want, it can be a web server. But it can also be a Tic-Tac-Toe console game written in JS (see for example this code).
1) Since you have to program config files, logs, HTTP etc. on your own, it's your decision, how things work and what you implement. Take a look at the different modules, like http, zlib,... , in order to find out which parts are already there for your convenience and which things you will have to write yourself.
2) Whenever you want to write a small (console) appliation, HTML-enabled appliation for GUI (e.g. Electron, which is used by Atom Editor and others), whenever you need a lot of IO operations or when you want to use socket communication over the web (e.g. chat application on your homepage). There might be more cases, but you should go and discover the world of Node.JS for yourself!
3) You cannot really compare a specialized application to a general HTML-preprocessor, can you? As for Go, why not make your own benchmark for your specific use case?
4) Application in JS with all the good stuff (front-end) developers have been used to for many years.
5) You do know how to google, right? Well, I can tell you that big companies have started adopting Node.JS. Source: Me, since I work for quite a big one. Also Microsoft is all over Node.JS lately, seeing as they used Electron for their Microsoft Code Editor and all the support in Visual Studio. And, of course, Samsung: They even bought Joyent, the company behind Node.JS.