This car has little tubes, about 1/2" diameter and 3/4" tall, on top of the axle, near the ends and near the center. They have corks in them. Surely they are for oil - is this typical for an EX?

Not from what I have studied.
The original EX rear axle for my car was so rusted and pitted it was not worth using any part of it except the gears. But the bearing at each end of the axles would be very hard to grease. I can see the need for a modification.
I used sealed bearings with the type that has 50% thrust. There back to back at each end of the tube and preloaded when the wheel is installed. That way when you go around a corner the axle gear is not pressing against the ring gear.
Rolly

Good luck with the car I’m glad to hear it’s running well, it’s a beautiful car.