I doubt that this is a change the developer will make. The database only stores the term ID values for one and as a general rule, term names can be easily changed in WP.
I would build a function that gets the term ID that I’m looking for… get the terms in the taxonomy, look for the term and return the ID. Then I’d create an acf/load_field filter http://www.advancedcustomfields.com/resources/acfload_field/ and alter the taxonomy argument of the field. You can see how a relationship field is put together by creating on and then exporting the code. Any field argument that is shown when exporting a field this way can be altered during a load field filter.
I can’t help you with any login or other issues. This is a user support, users helping users. The ticket system is handled separately.
