I don’t use Jetpack so don’t have your exact environment. Turned out to be a bit more involved than I anticipated but I did some testing and this seemed to work to reposition the pagenavi controls:
1. Remove these two lines in your child theme single.php file:
<?php the_content(); ?>
<?php wp_pagenavi( array( 'type' => 'multipart' ) ); ?>
2. Insert the following block of code in the same place in single.php:
<?php //move the PageNavi controls above the Jetpack elements below the post content
//assign pagenavi code to variable
$pagenavi = "<?php wp_pagenavi( array( 'type' => 'multipart' ) ) ?>";
//get the post content
$content = get_the_content();
$content = apply_filters('the_content', $content);
//append pagenavi code to post content
$content = $content . $pagenavi;
//start the output buffer
ob_start();
//parse the pagenavi php code appended to the content
eval("?".">".$content);
//assign the buffer content to the content variable
$content = ob_get_contents();
//clear the output buffer
ob_end_clean();
//output the content to the page
echo $content . '<br>';
?>
3. The bottom border under the pagenavi page numbers is normally hidden by the content overflow setting. If you want to hide it in the new location you can try adding this to your custom css:
.wp-pagenavi {
overflow: hidden !important;
}
Hope that helps.