How to keep a huge cargo bike safe in the city?
I'm answering my own question because I took a combination of the steps above, plus some other steps.


I took steps to make getting it back in event of theft more likely: 

registered the bike with the Chicago police: https://portal.chicagopolice.org/portal/page/portal/ClearPath/Online%20Services/Bike%20Registration 
I plan to register it with https://www.nationalbikeregistry.com/ as well
Made sure the store I got it from keeps bike serial numbers on file
Rolled up an extra copy of the receipt, with my name and phone number on it, and put it inside the seat tube
Made sure it was covered on my renter's insurance

I figured out a hardware setup

Heavy chain (the Fuggedaboutit lock+chain) for locking the frame to a post, instead of the flimsy cable.
Tethered the seat to the frame with a small cable
Normal U-lock for locking the front wheel to the frame.

I'm hoping to deter based on looks also

Covering up brand-name info with a unique combination of stickers
Chose a bright, unusual color when I bought it