I think you missed the "CVT-RB" timing, which is specified by the "-r" parameter in the "cvt" command.
By forcing a "CVT-RB" timing, I manage to force the GPU to recognize my display as a computer monitor, instead of a flat panel TV.
But I think your <--set "Broadcast RGB" "Full"> is a better way to go.
For more info on setting timing mode on Windows: Graphics — Custom Resolutions & Modes