I just realized your gigantic post is actually a quote of my first post :P
So basically what you should do is get the most recent Nokia Suite (possibly a beta one) so it detects your N9.

After it's done loading the content from your phone, go to the last symbol on the top, it should have a yellow exclamation mark (!).

After you click, on the bottom left you should see "Phone and Tools" or something like that.

After clicking there, wait until the top right symbol of the phone stops "Updating" and click on "Make space".

It will tell you (most likely) that you have over 2 thousand (2000) messages on your phone, and that you should move them to your computer.

In my case, I had 14,6k messages, which were a mere 4,6MB.

You need to be calm, as this will most likely take a very long time to get done... (I usually have to wait a few hours, with my phone connected to the PC until it finishes "Updating")


Later,
Chinoman10.