I'm not sure if you need the recordset rsgetnews at all.
Try updating the references on the page to use the URL parameter directly like:
echo WA_getCMSContent($database_PowerCMSConnection, $PowerCMSConnection, 'NewsPosts', 'Headline', false, $_GET['ID']);
Also if you used the URL parameter "NewsPosts" instead of "ID" it would work automatically.