Deep integration with (Zend) php project

Hi,

We have a large project built in php 5.2 (we use Zend framework), and we would like to integrate wordpress with our running code in order to:
– allow our users to post articles (blog posts in specific categories, with comments and all the cool wordpress features)
– use wordpress in order to build a simple questions & answers feature by using a commercial theme (from templatic)

Our problem in both cases is that we need deep integration with wordpress:
1. Single sign on using our authentication methods (we will disable the registration and login features in the wordpress installation)
2. Use our user data in wordpress: user names, descriptions, avatars, and other profile data with links to the profile pages of our site
3. Track posts, comments and other activity from users in order to present summaries in their profile pages, use them in our internal “user ranking” calculations, etc
4. Use our own rich editor for creating new posts or embed the wordpress rich editor to our site (without the rest of the admin features)

I searched, but I could only find simple solutions for showing posts or user data, so I would appreciate any help you can give me.