1) The security check at DKR is a TSA requiredment. Nothing to do with DKR specifically!
2) SAA have put the stop back on IAD-JNB so now runs IAD-DKR-JNB again just like JFK-DKR-JNB. The weight penalty is costing too much with the current fuel prices.
3) Delta will not put a 777-200 LR on the route since it cannot to MTOW out of JNB due to tyre speed restrictions. They were going to upgrade capacity by using a 777-200 non-LR but they have chosen to start JFK-DKR-CPT instead and is timed to connect with ATL-DKR-JNB. Using a non-stop on the ATL-JNB leg would mess up the connections with the JFK flight!