Hey guys, sorry for the lack of updates. Life and stuff. Thanks for all the tips, texaskirbyguy! It's really helping to move the project along. The fan is still being difficult. This vacuum has been used as a commercial vac for at least some of its life so I suppose its possible someone else got into this motor and got a little overzealous with tightening the fan assembly.
Oh and yes, it does still have its original metal fan, with barely a scratch on it!