Ok, some of what you describe crosses with the rest. PHP-Nuke is a full-blown CMS in it's own right, giving each of it's users their own Blog within as well as the forums (PHPBB2) that are built in. If you want PHP-Nuke, there's no need for Wordpress to be used, in fact using both would mean that maintaining them would be that much more work for you. Wordpress can have PHPBB2 (or other) forums installed, but they aren't really integrated like the PHP-Nuke is.
My bid is for setting up PHP-Nuke for you to do the job you want without the unnecessary Wordpress.
I've done a lot of work with PHP-Nuke, including theming and customization.
Todd