In my first post, I mentioned that I had uncommented that line (it is a bit hard to find, buried in item 2b).  All of the testing mentioned here was done with that line uncommented.

I know I'm getting in on this late, but I have ran into some of these issues also and let me share how I tackled some of them:

Since we ghost all of our machines before we send them out, I change the settings in IE to automatically logon with current user login name and password.  I set this by default and then the users will be logged on to the portal when they hit the page. That takes care of the automatic login for when a user is on campus and at their machine.

I deal with the same situation here.  What I did to take care of this problem is that I added a SQL Trigger to the table that checks the fields after a user is created.  If the Email or First/Last Names are blank the Trigger fires and updates the fields.

Ok, try not to fall down laughing over this one, very simple and it serves the purpose.  I created an HTML page that does an automatic redirect to the login page.  Set the priority of how pages are access in IIS and made sure that index.html was the first page that was accessed from that site.

Hope that helps some.

Steven

Okay I might cover ground that you already have done but that's only because I've confused what you've done with another post.

Here's how I've got it setup on our intranet (and going by memory because I don't have my laptop home with me tonight to check my dev site):

1.I think if you remove the Integrated Security=false from the connection string it should work. Verify that your sql box takes connections in both modes (Windows Authentication and SQL).
2. Uncomment the <add name="Authentication..... or whatever it is exactly
3. Around the impersonation lines..... I left the DNN default and only uncommented the <identity impersonate... line and set it to <identity impersonate=true userName="domain\username" password="password" />. I ran into the same problems you did if I tried it any other way. Now, once you do that you may have to give that user the same rights as your ASPNET/Network Service account on your DNN install and possibly the Microsoft.NET directory in the Windows directory on your webserver.
4. All sites where I work are automatically trusted due to Group Policy.

Hope that helps a little bit.