Thank you for this intel, B747! Puzzling that the ET agent would be so wrong across the board, and not particularly encouraging as an intro to ET, hah. Do I have to do anything in advance, or just wait until our arrival in ADD to find an agent to facilitate this?

I wonder if you also have any insight into the following separate-but-related question: on our outbound journey to ZNZ, we couldn't get a booking that included the final leg, so we arrive into ADD on an open-jaw that later returns on the itinerary mentioned above. To get to ZNZ, we have a separate ticket, also on ET but booked as a one-way from ADD-ZNZ again about 12 hours after arrival. This one I'm sure we will certainly be on our own for hotel etc - but I am wondering if it may in any way be possible to get the ET gate agent perhaps in EWR to check the bag through to the final ZNZ destination? I imagine this is wildly unlikely, but man, if it were possible it would so simplify that layover and the yellow fever requirements of ZNZ.