I have a bunch of text figures that point to scattered images, and I would like to be able to cross reference them like Word can. However I can't seem to find any native functionality for this - are there other viable options?
In Out of the box SharePoint, it is not possible. However you can try using one of the below approache:
Promoted Links: You can use promoted links list. In this list you can add images and caption/description to image very easily. It will show image and its caption in fancy way.
Word document with Page viewer: You can add the images in your word document(which you already knows) and store this document in one of the document library on site. And show this document in page viewer web part.
Reference: How do I open a Word document in a web part