There isn’t a way that I know of to filter a post object field based on a selection in another field or fields, at least not built into ACF. A post object field is a select2 field and the contents of this field are generated by an AJAX request. Information from other fields is not sent in that AJAX request. There might be a way to alter the alter the request, but nothing that I can remember has ever been posted here about how to do it and I have not been able to figure that out. If you can figure out how to alter this AJAX request then you could use https://www.advancedcustomfields.com/resources/acf-fields-post_object-query/ to get the additional information from the request ($_POST) and alter the query.
More than likely, if I needed to do this in a hurry I would use a basic select field rather than a post object field and I’d build custom JavaScript and a custom AJAX function to allow me to filter the list shown in this field. I have an example of this here https://github.com/Hube2/acf-dynamic-ajax-select-example/tree/master/dynamic-select-example
