The clone TV device should have only 1 input (Antenna) and use Method 2 (discrete method) with "1" as the command. For activities not using the Antenna input, simply select the main TV device as usual. For activities using the Antenna input, select the clone TV device (instead of the main TV device), but add the main TV using the activity add device feature (Yes, but I want to add more control of options and devices for this Activity). When it ask what input to use for the added main TV device, select "I don't need to set the input on my main TV". Here, all you want the main TV to do is control the power.

Note 1: Did you check if the "InputNext" command in device mode skips the antenna input?
Note 2: You do need to add the Antenna input in the main TV device input setup (as mentioned in my previous post) although it can't get to it except on power up. Else, it will go out of sync. What a stupid Mickey Mouse TV user interface.