I think your issues may be resolved by changing the settings within your TV set. Look at your TV manual or find it online, and set the parameters step by step, especially the input and output. You will have to make the settings for EACH input (source) for example Computer - Cable Box - Apple TV, etc. if you use these.
Set the output to TV speakers. The Optical Cable will be plugged into the Oticon TV Adapter. When you switch to the TV Adapter Program either by ON App or press on Hearing Aids, you should hear the TV sound streamed to your hearing aids, and the sound will also be transmitted to the TV speakers. The TV speaker volume will be adjusted by the TV remote control and will not affect your TV Adapter volume and vice versa. The volume control is independent.
No need to unplug Optical Cable or use AB Switch.
If you plug TV Adapter into the headphone jack, only the TV Adapter will receive the sound. If you want to do this, you will need to get a splitter and plug in a speaker - like a Beats - for others to be able to hear the TV. Volume control is not completely independent.
The key is telling the TV what you want to accomplish on each and every input. For me, I want to output by optical Cable to TV Adapter and also sound out to speakers for others. When I watch alone, I mute the TV speakers sound (TV remote) and Mute the HA mics so only the streamed sound is heard in my ears.
This is how it works for my TV’s. You need to get the sound working on both the TV and the TV Adapter at the same time, then you will be able to adjust the streamed sound quality with your Audi.