when one pad on a caliper wears that bad, usually that means that the pad hung up and stuck in place and didn't return.
The most common reason for a pad hanging up is the that the sliding surfaces aren't cleaned and lub'ed.
The surfaces that the calipers rides on on the spindel and the caliper itself should be cleaned with a stiff brush. Hi temp lub should be applied sparingly to the surfaces.
The bolts that hold the caliper on should be removed, cleaned and regreased. Check to see that the boots that the bolts go in to are not broken and caked internaly with dirty and other muck.
Make sure that the bolts aren't bent.
Next could be a leaky caliper, or hose that's weak and expanding or internally swollen.
Also bleed the brakes. If there is a lot of water in the system, it collects in the caliper. That causes rust and the piston can become sticky during it's movement and may not return. Also the water compresses. . causing brake fade, uneven brakeing.
I've heard two reasons for Dodge putting on the spacer. Mine came from the factory with it on. I heard that because the same track bar is used on the 2500/3500 as the 1500... and that it should be a bit long for the 2500/3500... but it's not and causes the wheels to be a bit of center. So to correct for it they added the space to the passenger side wheel.
If I don't have my spacer on, my passanger side wheel is deeper in the fender well than the driver side wheel. With that spacer, the wheels are exactly in the same position within the wheel well. So that explaination made sense to me.
Other say it was for brake pull. I think someone even found the TSB for it. I don't get how it effects brake pull... . just don't see it.
If I take mine out, I don't get brake pull, and I just can't think of the dynamics that would be effected by that thin of a plate.
Try it, it can't hurt.