I do not use iTunes in conjunction with this container so cannot really give you any guidance. I simply point it at my music and audiobooks libraries that are held directly on unRAID (outside iTunes) and go from there. I configure the MyMediaForAlexa admin using the WebUI option available from the menu shown when you click on the running containers icon on the UnRAID docker tab. The only time I use iTunes (on Windows) is to copy music/audiobook files onto an iOS device, I do not use iTunes to store my media.
If you are holding your iTunes library on your unRAID server, what software are you using to act as the iTunes server on UnRAID? I could try setting that up on my own system to see if I can get it working.