The reason you saw "oil" leaking on your wheels is because the bearings overheated. Sounds like they were over tightened. Replace all bearings and races that were overheated along with new seals and grease. It is not normal to need done at 2,000 miles and one year old. Pack bearings good and smear some grease in hub area and assemble.
For the adjustment, here's what works for me:
Tighten nut with channel locks until real tight while spinning hub by hand. This sandwiches everything together solid. Now loosen until completely loose. Now use those pliers and snug up the nut EXCEPT tighten nut with pliers as the jaws face the nut from the front, not the side. I'm not sure how to say this, but we typically use pliers and wrenches at a right angle to the fastener to gain leverage. Don't do it this way for final adjustment, hold the jaws up to the nut from the front and turn the nut with your wrist muscles until it seats. I have found A person probably cannot over tighten the nut, tightening it without a leverage advantage. So now if hole lines up great but if I have to use any leverage that will be too tight so back off.
For what it's worth, that washers job is to keep the bearing from acting on the nut to overcome the cotter pin and loosen or tighten nut. All washers I have seen have a way to keep washer from spinning such as a notch and the spindle has a groove, match them up. If yours just has a round washer, then ok, it must work that way.
It may be interesting to mention that when adjusting hub bearings on semi trailers you always go to a light torque like 10 ft lbs then tighten until holes align (no cotter pin, different device, irrelevant). Much different than RV trailer hubs. The difference? Oil. Semi hubs are in a constant bath of gear oil as are ring and pinion bearings. When oiled this way they can be adjusted tighter. Similar is true with the full floating axle a 3/4 or 1 ton pickup uses, just not quite the initial preload.