Add this to the first php block:
$length = 40; // adjust to needed length
$thiscomment = $comm->comment_content;
if ( strlen($thiscomment) > $length ) {
$thiscomment = substr($thiscomment,0,$length);
$thiscomment = $thiscomment .' ...';
}

Then instead of using:
echo $comm->comment_content;

Use:
echo $thiscomment;

Hope this helps everyone!