Hi,
I collect American Flyer O gauge and it is great that you have your father's train. I am not sure if you know this or not, but the cars in your father's set have been repainted. I noted immediately, that the cars are not a standard Flyer color for this type of car and was suspect over the shiny silver wheels and good condition of the gray trucks; however, when you turned the one car over to show the power pickup, I was able to confirm the repaint. I noted that the tab going from the car bottom to the power pickup on the wheels has paint on it that is the same color of the body. That should not be the case as when made at the factory, the cars would have been painted and then the light socket, tab to the trucks and trucks would have been put together after the painting of the body. Another feature that is incorrect is the railing of the observation car. That should be either brass or brass painted steel. They were never the same color of the body, which signifies that when the observation car was repainted, the observation railing was not removed. Additionally, although the video is not great for the details, it appeared as if there were dents and bends to the body and roofs, without associated paint loss, another sign of repainting.
The tender appears to have some restoration, as the body of the tender appears to be held on by nut and bolts and the box at the front is painted black instead of being painted gold. It may be that only the trucks and wheels on the tender have been restored, but I cannot say for sure.
The engine appears to be repainted as well. I noted that the trailing trucks on the engine appear to be from a post-war Lionel engine.
As for the running of the engine, it does want to run and it has plenty of power, so don't burn it out. It may need a cleaning and lube. Another thing to check is the brushes and armature to see if the armature is dirty or the brushes need to be replaced.
Overall, it is a great family piece and if your father had it restored, it is because it was his prized possession.
The set likely originally looked like the set below
NWL