Is there a way to change content in 1 master node and have it changed in hundreds of others?
If you have so many blocks, then you should try to find ways/techniques to reduce the amount of them. Below are some possible modules to help you on that.
BEAN
You should have a look at the Bean module, which potentially can help you to answer this question. 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.

This module also works great in combination with the UUID and UUID Features Integration modules. And after you become familiar with the Bean module, you might find other cases in your site where you also want to use this module (which somehow compensates the fact that you need to add another module).
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.
Remark: this module (a raising star!) has been moved to core in D8 ...
Rules and Rules block visibility
Another module to have a look at (to help reduce the number of your blocks), is the Rules block visibility module. Here is a quote from its project page:

The Rules block visibility module allows Rules components to be used to control block visibility. This provides Drupal administrators and developers extreme flexibility in controlling when blocks should be displayed on their websites, in addition to the default visibility options provided by Drupal.
The general idea is that if you can do it with Rules, you can use it to control block visibility, so the possibilities are limitless:

Need to show a block only for users registered more than a month ago?

Perhaps you have a block that must be shown only between 8am-5pm on weekdays?

What about displaying or hiding a block based on current weather conditions?


All of this can be done by using Rules block visibility.