Sorry you are correct, I just tested it and what you need to do is un-mount the Target then you can remove the connection from the server at SETUP -> iSCSI Initiator -> Portals -> and click on the disconnect and remove the IP Address from the portal so it does not reconnect. Then re-enable the Target on the DSS then use the SETUP -> iSCSI Initiator on to connect to the Target via it's own IP Address (dont worry about the message as this is only temporary to get your data restored).

Sorry about the write doc on this as this is an explored idea on how to get your data restored and is unconventional from our practices but I tested it and works - let me know how it ends.