Dear A 300 Man, its seems like you really have a disconnect between your questions and your profile. My post is slightly off topic, but I thought you wanted to speak to me on my flight, like you have announced in the ME forum. “I have many questions for you” I would have been happy to answer your questions on board, but you never showed up. Just for you information there is no F class on flights to MNL. I think the nature of your questions is based on experiences you are doing as a cabin crew, being sometimes placed at R2 or in the middle of the airplanes or at the back.
Nevertheless I will answer your questions best I can:
1. The engines idle back while encountering the turbulences because the pilot has to fly a certain speed, usually lower than the cruising speed (A 330 cruising speed is 0.83 and turbulence speed 0.80) which provides structural relief and prevents structure from being overstressed. That’s why you hear engines idling back.
2. To spare a long technical explanation, its got something with the momentum, as john_tullamarine said, the momentum at the rear is greater than in front, because the same force*grater distance= grater momentum.
3. Agree with john_tullamarine, the general rule is one aircraft length. Its also a matter of pax comfort, to keep reasonable distance in order not to intake fumes from preceding A/C.
There is nothing wrong with being a cabin crew. If you still want to see me on board of one of QR A 330, mostly welcome.
Cheers.