1) The camera does not move in ZBrush. Now if you’re referring to how the model will rotate around the last stroke, that is disabled by turning off Transform>Local. If you want it permanently disabled, turn it off and then press Ctrl+Shift+I to save your settings. The model will then always rotate around the geometric center of the model or whatever the currently set pivot point is. There are times when Local is a huge help, though, such as if you’ve zoomed in close on part of a model and don’t want the detail area flying off the screen every time your hand twitches.
2) The keyboard shortcut is currently hard-coded into ZBrush and cannot be changed.
3) This can easily be done with a simple ZScript/Plugin that would create buttons for incrementing and decrementing the value by whatever factor you want each time they are pressed. The buttons can be assigned hotkeys. This is exactly how the bracket keys are currently used to change Draw size – it’s a plugin found in the Zplugin palette.