Hi @tazintosh
I think you are correct. In this case, you need to set the choices dynamically, based on the value in the database (and the gallery if you want to). To do that, you need to use the acf/load_field hook. To learn more about it, kindly check this tutorial: https://www.advancedcustomfields.com/resources/dynamically-populate-a-select-fields-choices/.
I hope this helps 🙂