Thanks - I found two squint blades. One to be bent up and one to be twisted. That seems to have made a lot of difference. I can't get weights to do much, maybe I don't need weights.
I've also reversed the direction of turning - seems to be quieter that way.
Even at minimum speed, the motor hum still pulsates slightly, even though there is no visible wobble at that speed. Perhaps the motor bearings or something else inside there isn't perfect. I'll leave it at that.