Gear down and at least partial flaps would be a normal configuration to cross the final approach fix for a circling approach in most planes, I would guess that is the case for the SD-330. It is indeed a high drag configuration with little altitude for recovery if you do stall. But, you are in that situation every time you land a plane, right?
FlightGlobal have published an article with a security video compilation. If the playback speeds are correct, the aircraft appears to me to to be going like the clappers in a diving spiral. It looks similar to the FO's text descriptions of how the PI handled the aircraft when they had the undercarriage problem: steep bank and dive.