To fix my no communications issue, I connected the 2 pairs of CAN wires at the Front Control Module. I don’t know where that second pair of wires is supposed to be connected, but jumping it to the first pair of CAN wires made the system communicate.
But the engine still would not try to start.
Fast forward to this weekend and I made some more progress . I had previously not connected the ECM C1 pin 30 (yellow wire, "FUSED IGNITION SWITCH OUTPUT (START)") because I was not using the ECM to trigger the starter relay. Apparently the ECM needs this input to know when the engine is being started (as opposed to just providing fuel & spark based on cam & crank signal inputs).
Now it starts (mostly) and I’ve got some drive-ability issues to sort out.