1) Display of taxonomy fields is covered here https://www.advancedcustomfields.com/resources/taxonomy/. You can’t use the_field() with this type of field.
2) You need can use tax_query if you are saving and loading terms. Otherwise you need to use meta_query. For the meta_query you need to search for the Term ID in a like query. See this page https://www.advancedcustomfields.com/resources/query-posts-custom-fields/ 3. Multiple custom field values (array based values). In this case the values to look for will be LIKE "'.$term_id.'"', note the quote marks (“) around the term ID.
3) Not sure what you are looking for on this
...How do I get the field displayed as a inputable dropdown on the front end...
