it feels like theres something wrong with your vsync.try modding the settings in your nvidia control panel under manage 3d settings vsync.Maybe setting it to adaptive might help you.

looking at the fluctuating GPU usage (it's waiting for data), there seems to be a bottleneck in some other part of your PC. How's that CPU doing?

GPU load is all over the place.....try capping your frame rate to maybe 75fps.