Dynamically adjust argument or filter to views entity reference filter based on value from select list in form
The simplest answer ended up being to use Entity Reference View Widget which allowed me to build a view for selecting the entity desired.  This was nice because it allowed me to add some additional information and filtering the the approach I was hoping for in my question didn't allow.  Unfortunately, it also moves me further from being able to update this site to Drupal 8 because this module doesn't exist for Drupal 8 because the maintainer decided to let another module that isn't released yet, cover this functionality for Drupal 8.  I would still welcome answers about how to do this in a more forward compatible way.