Yes, checking the box is the same as dialing *72. The box below it is where you would enter the number to be forwarded to.
Theoretically, once you enter the info from the phone port, it would be visible from the Expert Configuration.
You do have to uncheck the 2 boxes on the right and then you can change the setting. You can play around in there all you want and the changes will not be made until you choose "submit".
The reason I said you would need to delete the item from your Obitalk account is:
resetting the device will remove the configuration from the device, but if any of the configuration still resides in the portal, it will just put it back on the device once the portal communicates with it.
You could access the device directly and temporarily turn of auto provisioning so the portal will not make any changes. Then manually make the changes to the "CallForwardUnconditionalEnable", reboot, then remove the changes. At that point check to see if forwarding is still occuring. Theoretically, again, there should be no way the device should forward without the CallForwardUnconditionalEnable checked and a number entered to forward to.