The DPDT switch that your using looks something like my diagram below on the inside. The slider will connect the right side middle pin with the upper or lower right side pins, and the left side middle pin with the upper or lower left pins. With the loop connecting the lower pins and the switch in the down position it allows the distortion to pass through. So you can kid of see how its not working.

All you need is a simple SPST switch. It will have 3 pins on it. Connect the center pin with the input jack. Then put the wire from the output jack on one of the outside pins and the distortion wire on the other. Or you can use your existing switch the same way and ignore one side of pins.