So long as every listing has a feature_posi
field (even if it’s empty), you can let WordPress/MySQL handle the ordering for you:
$args = array(
'post_type' => 'listing',
'posts_per_page' => -1,
'orderby' => 'title meta_value_num',
'order' => 'ASC',
'meta_key' => 'feature_posi',
'tax_query' => array(
array(
'taxonomy' => $taxonomyName,
'field' => $term_slug,
'terms' => get_queried_object()->term_id,
)
)
);