I want to move this, but can't find any way for deleting the existing dataset as I get a "cannot unmount mnt/APE_Pool/Adrian/syslog: device busy" message.
Try to run this from command line (either console of SSH, do not use the web GUI shell):
[panel]service syslogd stop
service nginx stop
zfs destroy APE_Pool/Adrian/syslog[/panel]
And then reboot -- you can just type "reboot" in the shell.