[Kevin Sevcik]

dynamic braking will NOT stop backdriving. This has been conclusively proven many times. Dynamic braking doesn't apply any power to the motor at all. It simply makes the motor more difficult to turn if you aren't already applying a voltage to it.
The way it works is that it shorts the leads of the motors together when the Victor isn't applying power to the motor. This creates back-EMF when the motor is spinning, but does absolutely nothing while the motor is at rest. Try it with a drill motor or CIM. Spin it by hand when the wires aren't connected, then have someone hold them together and see if it's harder to turn it.

to answer point by point:
1. No, it will not affect the normal operation in the slightest, though if you use it on drive motors, your robot will stop MUCH more quickly as opposed to coasting.
2. Yes, it work in both directions, but doesn't stop backdriving.
3. It draws ZERO power.
4. No, it will not stop your winch from slowly unspooling at the end of a match, AT ALL.