Thanks for the suggestion -- I had not tried that. With the TX/RX set to 433.9 I could hear but not be heard. And the autocal never got past the first scan.
I changed the TX/RX frequency to 431.150, and now I can send and receive Kansas City-wide using C4FM and my FT-70. Awesome!
Later in the week, I'm going to try and join a D-STAR net using my FT-70 and the Open Spot 4 pro. I'm going to be extra thrilled once that works. I want to take part in https://www.nebraskadstar.org/repeater-details/ because my local club uses that for some nets.