I do not know what you are talking about. Ailerons have absolutly no effect while taxing. Now once you come up to speed on the take off roll they can help you maintain level wings. Are you sure you are not talking about the rudder.
Well in either case there are settings in the aircraft cfg file that you can tweak to help to either increase or decrease the effect of a moveable surface. If you are having problems with a joystick I would first check to make sure you have the latest driver for it, then make sure it is calibrated correctly. Some joysticks are noisy and can cause some strange things. Make sure you read any help or readme file that might have some info on this. Also make sure the joystick that you are using is supported by both the system and windows you are using as well as FS

Not always. In stiff winds you will need to use your ailerons to keep the plane level when you taxi. The formula is when the wind is to your front you dive into it. When the wind is on the back of the plane you dive away from it. The sim actually doesn't represent this quite like the real world.
I tried an experiment and set my wind speed to what would be considered a stiff wind in a Cessna and there was little effect. The plane listed to one side when I set the controls wrong but overall I've seen heavy instructors make the plane list that much (or is that because of the landing gear damage from students plunking it down too hard ;D).
Now when I set the wind speed to a level that no RL pilot would try to fly in, I found the effect much more pronounced.
The only thing different was when the airplane is directly sidways to the wind and sitting still. Even wind speeds of 99 kts and the plane sits rock steady. In reality this would probably flip a small plane like a Cessna over unless it was very well tied down. It would possibly even do some damage then.
Of course when I set the wind almost to the max ACOF can simulate that's where the fun really began. Try it some time. Set the wind directly down the runway at about 99 kts and in the default Cessna try to take off. Actually you won't need to try to take off. The airplane will lift off without any help. Add some power and you have a hovering Cessna. Now try to land without crashing. That takes a little more skill. ;D
