FWIW. The particular bike is best suited for PAVEMENT ...
Actually I'm not kidding, a bike with a bend in the frame from the factory will more than likely bend at the bend in an accident, it's a proven fact even admitted by bike manufactures if asked. In this case the bend is in the front, if a there is a front end accident with something, say a curb, that is the first place it will continue to bend because the bend is already there ready to bend further.
Actually due to the bend in the frame it's unlikely, though not impossible, that the fork would fail first. The head tube is likely to fail due to the bend on the main tube allowing the head tube to be pushed back, so yes you are correct about the headtube, but the headtube is considered to be the frame. Which would fail first the headtube or the downtube? It doesn't matter since both parts make up the frame and thus regardless the frame is toast. If the frame was made correctly then the fork would likely fail first, then it's a good possibility that you could replace the fork and still ride the bike because the frame would not be toast. This is something that hasn't fallen on deaf ears in the motorcycle world, BMW was the first to design a motorcycle with a fork that was designed to fail allowing two things to happen, one was to attempt to lessen or prevent damage to the frame, and two was to increase the chance of launching the rider up and over a car instead of into the car and lessening injuries. If a bicycle fork is not over built the fork would bend back, or in the case of carbon break faster to taking some, if not all the stress off the frame. Obviously if the crash is severe everything, the fork and frame would be toast.
