Are you able to send me a live link/URL to your search page so I can take a look?

You could make it so using custom javascript. If, in that hidden field, you enabled the count setting, in the form ‘city’ would have the counts. Your javascript would then update the counts in the city section from there. Not something we can help you with, except for the trigger part of the code.

If you have Auto Count enabled, after the fields in the form update, your script would look like this:

<script>(function ( $ ) {
  "use strict";
  $(document).on("sf:ajaxformfinish", ".searchandfilter", function(){
    // run your code here
  });
}(jQuery));</script>

After the results update using Ajax, your script would look like this:

<script>(function ( $ ) {
  "use strict";
  $(document).on("sf:ajaxfinish", ".searchandfilter", function(){
    // run your code here
  });
}(jQuery));</script>

In V3 (due in a few months), you would be able to place the city field from the form in that header, and so avoid all of this.