Ok, turns out I was way overengineering this. The simple solution is to put he PHP block INSIDE the element that the AJAX results load into. Like this:

<div  id="ajax-results">
<?php

	global $searchandfilter;
	$sf_current_query = $searchandfilter->get(12192)->current_query();
	echo $sf_current_query->get_fields_html(
		array("_sft_travelmonth","_sft_destination", "_sft_activities"), 
		$args
	);
?>