@ryangodammit If I have understood correctly, depending on your system resources you could use Libreelec on the Chrome box as a media server:
1. Use out of the box drive mapping when USB media is mounted (Automatically)
1. Enable Emby plugin & configure your media libraries
2. Enable docker & install Emby - you can also use other docker images if required
Option 1 will work but is limited to how you have arranged your media and you will need to add the media locations on the firestick
Option 2 (Recommended) as a simple out of the box solution if you haven't used docker before. You can then connect to Emby via a browser / app to view your libraries, note within Kodi (Firestick) you can use the EmbyCon plugin to browse the libraries
Option 3 Docker, will use some additional system resources but has the benefit that you update the Emby version more frequently, however you will have to configure drive mappings, network settings etc
All depends on your IT knowledge.
Hope that helps.