The nicks on your strop, pictured, are no big deal. This is likely a case of your fear causing greater problems. Just relax and keep the blade moving. All you need to do is practice turning the razor at the correct moment in time. That moment is before you get to the end of the stroke. Then land the edge of the razor on the strop after the razor begins moving in the opposite direction.

Stated another way, the razor only touches down on the strop when you have a commited motion and direction. The edge NEVER touches the strop anywhere near the turn/flip.