We don't truncate the short description on the front end catalog page, but we do truncate it on the admin product results page. If you want to remove that limitation, you can change this line of code:
<?php echo substr(strip_tags($ProductShortDesc), 0 , 53); ?>
in the admin/products_results.php to:
<?php echo strip_tags($ProductShortDesc); ?>
In regard to the learn more button, can you please post a link to the page. It might have to do with the short description missing an end tag.