You will have to add a field in the modules parameters to add a target..
In your modules mod_j51hover.xml add the following just before </fieldset>..
<field name="target" type="text" default = "_self" label="Target" description = "Target"/>
In your modules mod_j51hover.php add the following just after $HOpacity = $params->get('HOpacity', 0); ...
$target = $params->get('target', '_self');
And finally further done on the same file replace the following...
<a href="/<?php echo $hover_link; ?>" class="info">Read More</a>
With...
<a href="/<?php echo $hover_link; ?>" target="<?php echo $target; ?>" class="info">Read More</a>
I haven't actually tested this so you might have to get back to me if it doesn't work
Ciarán