Great, thanks!
Well there are good news ...and there are bad news!
Your EMMC is working just fine: lshal shows that hal is picking up all of the partitions. Your MyDocs partition of 27GB is 50% free and is mounted without errors.
But your rootfs is almost full (96%), partly because optfs, aka. /dev/mmcblk0p2, is not available.

My advice would be:
1. Make a backup of all possible items in the in-built Backup application, especially the application list.
2. Format the partition /dev/mmcblk0p2 with3. Flash the firmware to make it use your freshly formatted optfs-partition according to this wiki-article http://wiki.maemo.org/Updating_the_tablet_firmware . Only flash the fiasco image, i would suggest to use a Debian- or Ubuntu-based Linux-Live-CD, which you might also use to enlarge your optfs to the desired 5 GB later.
4. Use the Backup application to rebuilt your applications.
5. Now install backupmenu to the N900 from the application manager of your choice
5. Resize optfs (Enlarge) to 5GB and MyDocs (Shrink) to 24 GB according to this wiki-article http://wiki.maemo.org/Repartitioning_the_flash . Do not use one of the Manual Solutions #1 to #7. Although they still may work, they are fairly outdated. Either use the part 'Using gparted' at the beginning of that side or use Solution#8The GUI-Solution at the end of the side.

And: Do not hesitate to ask for more information for any of the steps or if errors occur again!