You guys are great - thanks for all the help!
Order to the Train Tender is going in the mail tonight. They had a number of other parts that I decided to pick up since this thing is apart, including new brushes and springs, a new proper screw for the front truck, the thrust washers needed to shim the axial play out of the armature, etc. I had never heard of them before, and will likely be going back when I finally decide to get some of my old accessories working again. Thanks for the suggestion TheGandyDancer.
I am starting to suspect that the reason for the rough running and high current draw was excess axial play in the armature, which was causing the armature to shift which bound the gears. As I remember it ran fine in reverse, which would make sense. I will post the final findings after the parts get in.
Thanks again for the help everyone!