Let me chime in.
As to question 2. The answer is "Yes", no signal is sent to the primary amp when only the 2nd zone is used.

Question 4. The multi button is active on the remote as long as the 950 button is active. The multi button is dual purpose I believe it also is labeled T/V. I don't have the remote near me at the moment. The only difference between the primary zone on or off seems to be no OSD when the primary is off.

Let me add, I have a 7 channel amp and use 5 channels for home theater and the other for the remote zone. I use one (1) trigger cable and it works fine.