Fan Tapered Hub Damage - help with cause and repair

[Diastole]

To anyone with advice,

I changed my water pump the night before a parade d/t a leak. Installed my working, relativity new, cast aluminum two-blade fan. The taper on my backup water pump was such I needed to add a washer behind the castellated nut to seat the fan and nut correctly.
The fan and water pump worked great for the 12 mile highway driving to the parade, and all thru the parade. But on the way home, a terrible screeching, rattling, grinding noise came from what sounded like the front of the engine.
On inspection, there was aluminum powder on the back side of the fan hub, see picture. The fan had a little sideways movement, <1/8", but turned with the engine.
The engine ran well. The water pump has sealed front and rear bearings and has been lightly used. The belt was appropriately tight with 1/2"-3/4" deflection. No cooling problems.
The tear-down inspection of the fan and water pump revealed the water pump is in good condition. Both bearings solid and without significant runout or wear, see pictures. The shaft is centered without runout.
The taper on front of the water pump shaft has a GREAT DEAL of new scoring, gouging, grooves, and wear, see pictures. When I removed the fan the woodruff key was lying on the bearing, I am unsure if I knocked it out, or if it had been dislodged prior to my disassembly, see photo. It appears that the tapered shaft to fan hub is the source of the horrible sound.
Tried to replace the fan on the tapered shaft and there is too much wear, slop, and movement. It appears to this novice that the woodruff key somehow came out and the fan and shaft rotated without the key.

See pictures

The tapered hub of the fan is shot. Any ideas how to fix it, where can I get a new hub to press in? I do not want to buy a new fan - hub assembly.

Do any of the FordBarn Experts have any other explanations for the problem? Remember the water pump is perfectly normal, except no paint on front end due to the wobbling fan scratching it off.

Thanks in advance,
Diastole in the Smokies