Has no one noticed these lines?? There obviously is not enough space in /home:

/dev/mmcblk0p2 2.0G 1.7G 189.1M 90% /home
/home/opt 2.0G 1.7G 189.1M 90% /opt

189Mb free. Do you have any huge games installed? Like Kroll or Preenv games or Wildlands etc? Those are eating your space. The N900 by default has only 2.0GB partitioned as ext3 for games and applications. You can increase it using several methods posted here or the easiest way would be a custom eMMC image (solution 5). You could backup using backupmenu, flash and restore.