to second:

The not starting backupmenu is installed in the opt partition. There are different ways to do this, maybe you can ...

... boot from a linux live-cd or install ubuntu into virtualbox (it has usb 2.0 support).
- boot the n900 into backupmenu and activate USB Mass Storage Mode.
- convert the opt partition from ext3 to ext4 without losing data with tune2fs http://www.thegeekstuff.com/2011/05/ext2-ext3-ext4/.

or

... boot into Backupmenu and go to root console (t).
- use parted ... print all and look for the partiton number, normaly /opt is mmcblk0p2.
- mount /dev/mmcblk0p2 to /tmp/mnt/optfs
- mount an ext3/4 partition (from sd?) to /tmp/mnt/sd
- copy -a * from .../optfs to .../sd
- format mmcblk0p2 with parted to ext4
- copy -a * back from .../sd to .../optfs