I only want to display all the forums, descriptions, # of topics and # of replies (similar to how the forums are displayed on the sub-domain forum home page)
This plugin doesn't in my understanding have a feature like this, so you need to do some custom MySQL query to the miniBB's database and write some code...
AND - how can I use this plugin if my forum is on one TLD and page I want to display is on another TLD?
The contents of this plugin will be available publicly in http://www.somedomain.com/forums/addon_1stpagenews2.php or something like that. You can fetch that page with PHP for example. Here's a code example:
$stuff = file_get_contents('http://www.somedomain.com/forums/addon_1stpagenews2.php');