Hi Todd!
So, finally I created a 10 GB iSCSI volume and mounted it via WAN on the source dss. The backup db is saved on this iSCSI share and the backup to the Dynamic Volume has been through this night.
How Do I now savely remove the iSCSI volume, without deleting the backup DB?
Normally I would unselect the backup function, then remove the LogicalVolume and finally use the CLI Tools with Ctrl-Alt-X to remove the partition vg02 (and restart).
While doing the restart, I could also pull the USB cable of the DynamicVolume.

Will all the data be preserved with these steps?
Thanks again for the feedback!