InfoPath Dev

Hi -

I have a requirement that I've not run across before and hope someone has some tips that might help me work thought it.

 I'm on SP Enterprise on prem 2013 / IP 2013. I have a simplified example to illustrate the issue. I'm not a developer but am comfortable copying/pasting code with detailed enough instructions. I hope the solution here won't come to that. :D

 The first iteration was:

1. A List with 4 columns. (The list is used for many things; the IP form connection is just one facet, so having just a form library with no list is not an option.) 
1. Name (Title)
2. Category (default Choice)
3. Color (default Choice)
4. Description (single line text)
2. Form Library / Form
1. Data Connection to List which pulls all 4 columns
2. Category field / drop-down control; choices are from Category column in Data Connection
3. Name field / drop-down control; choices are from Name column in Data Connection, filtered based on selection in Category
4. Section, hidden by default, with all 4 columns displayed in read-only text boxe
5. The user selects a Category (Fruit or Vegetable)
6. The user selects the Name of the list of fruits or vegetables now in the drop-down
7. A rule unhides the section, and default values populate all 4 controls with data from the List, based on selection in Name

All of this works fine. So here's the rub:

Users want to make Category a multi-select choice column. Tomatoes can be categorized as both Fruit and Vegetable, so they want to be able to pick both in that case. (NOTE:  In the actual system I'm working with, this field will probably have a dozen choices.)

If I make the change in the list, and make multiple selections on an item, then that just becomes another choice (with # sprinkled before and after the terms).  What is desired is that ONLY the single choices be available in the drop-down, and if Fruit is selected, Tomato is a choice in Name, and if Vegetable is selected, Tomato also appears as a choice in Name.

Ideas?