How to manage text on my site that's not node content?
Consider using the Bean module for this. Here is a quote about its project page:


  Think of a Bean as a method to provide new types (compared to node this would be a content type) which then provides an add content interface to create as many blocks as you require (see screenshot below). The bean content can then be placed around the site just like any other block.


If you'd grant content editors the appropriate Bean permissions, it appears to me that you might be close to a possible solution to what you're looking for.

The video tutorial Drupal Bean module tutorial - using Bean Admin UI provides a great introduction to really understand the power of this module, and the kind of things you can do with it (by only using site building techniques, no custom coding involved). It also shows how the Bean module transforms Drupal blocks into fieldable entities.

PS: This module only started as of D7, and is already integrated in core in D8 ...