I agree with the previous comments. Adding 50ft to the MDA only applies in the case of a CDFA, to avoid descending below MDA in the event of a missed approach. The 50ft additive is not required by all regulators, and I have never heard of it being applied to the circling minima. Seems a bit pointless for a circling approach, as others have already said.
Regarding wind corrections, my understanding is that the turn radius used to calculate the circling area is based on the aircraft's TAS plus a 25kt wind factor. The circling area is then defined by a radius that is twice the turn radius plus a fixed straight segment, centred on the runway thresholds.
The 25kt wind factor is only used for the purpose of calculating the circling area. When flying the approach you still need to turn base at the correct point on the ground and adjust the downwind timing accordingly. In nil wind that point is typically 3sec/100ft of altitude. For example, if circling at 1000ft in nil wind, the base turn point would occur 30 seconds after passing abeam the landing threshold. The turn point needs to be corrected for wind to ensure the aircraft turns at the correct point.