Did you try adjusting the code that I posted above?
To change the currently selected value what you want to do is to look at acf/load_value http://www.advancedcustomfields.com/resources/acfload_value/
so you’ll have 2 filters, one that sets the choices in load field and the other that sets the values in load value.
The only problem with this is that the value won’t change should someone choose a different term. What I would do is to not display the taxonomy box on the right, not sure how you’d do that. Then what you’ll need to do is also create an acf/save_post filter http://www.advancedcustomfields.com/resources/acfsave_post/ and also update the terms for the post yourself as well.
