Don't use the FX loop on the pod.
Have the FX send on your amp go to the guitar in on the pod. Then have the 1/4" out on the pod go to the FX return on your amp. There is no need to create an FX loop block in the pod.
guitar -> tube amp Input -> tube amp FX SEND -> POD guitar in -> [ ambient effects ] -> POD 1/4" OUT (L or R) -> tube amp FX Return
Obviously, make sure you have an empty amp block. This is definitely the easiest way to do it . I do it all the time.