I suggest you keep that
Tektronix 466 oscilloscope.
You'll eventually learn how to use it if you hang out with us.
Regarding a "big dish", I'm not saying to put that first, as you do have other projects, but I recall a wonderful BUD you found on vacation last summer, and I still think that could be fun for you...
... and the envy of us all! -

- it was a hell of a dish! -
During your recent absence, we've had a discussion of
OTA antenna.
They may be too small for your needs, but some interesting home-brew info came to light in the thread.
As for motorizing your FTA dish, ya need to get back to that thread and see it through to completion.
K'bick posted a
picture recently (4th pic) showing his dish mounted to his motor.
It reminded me of your efforts, and I think worth a look.
My first thought was that the dish was too far down the motor shaft, much as yours would have been with the mount you ordered.
However, read his thread - it offers some good encouragement, and apparently he had success. -
PS: has the dish farm drained, yet? -