Well, there are web sites that purport to rate speech by grade level. You just need to provide some text.
So, here is Joe 27 years ago setting "Frank" straight about Joe's IQ:
https://www.youtube.com/watch?v=D1j0FS0Z6ho
Do start transcribing, and tell us the resulting grade level.
Might be hard since Joe has been known to plagiarize speeches