Is there any other way to create a "settings" node without having to create a Content Type?
The clean way is to create a custom module or theme with settings you need.  Examples For Developers shows you how to do it. 

If you need settings, you need them because something will use them. So just adding a proper form shouldn't be too big overhead. And if you keep your settings in a way that makes possible for field to cease existing, you need to add more lines of code to safeguard against such situations. You don't want that. It's disaster waiting to happen.