I agree: it looks like a crude link for a Panhard rod.I would remove it since it may be somehow contributing to this problem.
The wheelbase of your car is 80" when its sitting on the ground.
In other words, center of front wheel to center of rear wheel should measure 80".
Assuming the front wheels are positioned properly (no excess wear or bent A-frames, etc), you can use this number to check the correct postion of the rear axle centerline.