Just use DTV in the linkroom.
AV-DTV gives you the sound from the DTV in the mainroom.
Link DTV is used when DTV is already used in te linkroom with another source.
DTV gives you the both sound and video from the the mainroom (but only when you haven't used DTV for another source/connector in the linkroom). That's why option 6 is used, if it doesn't exist in the linkroom, it uses the mainroom source.
When you have sound but no video after using DTV, then check your linkfrequency.