I don't know FreeNAS, but is there really a directory called "//Disk-1/nUll/Backup" accessible if you were to login to like "ssh user@10.30.2.161". I doubt it. I suspect you want
# rsync -v -e ssh usr/ user@10.30.2.161:/Disk-1/nUll/Backup
or
# rsync -v -e ssh usr/ user@10.30.2.161

isk-1/nUll/Backup
You may not need the "-e ssh" based on the config file.
[[ sorry that's a colon followed by one or zero slashes, not two slashes ]]