Which is kind of the point I was making. A largish object is photographed across the tracks and appears to have been removed from that location very quickly. There does not appear to be any photographic evidence of the type of heavy equipment used to lift rails, repair or realign the track being used. That would have taken a while to get to the scene and remained for some time while any work was completed. This does not appear to have happened, which suggests that the damage done to the track was insignificant as far as affecting trains running along the lines. Railway repair work and the heavy equipment involved generates some good photo opportunities which would not have been missed by journalists at the time.
So we are left with the conclusion that whatever was left lying on the tracks was fairly large, yet relatively light weight. The tracks suffered no damage sufficient to cause them to be relaid, so impact with the angine and gearbox can effectively be ruled out.
We can be certain that some part of the aircraft struck the embankment because of debris left on top. Prop marks show that at least one of the engines was turning and developing power.
I suggest that the evidence indicates that it was engine four that created the marks and that the force of the propellors striking the embankment in addition to stresses caused by the wing tip being torn away, caused the engine to separate from the wing in advance of the rest of the aircraft impacting the ground. That would account for the engine being found away from the rest of the aircraft. Everything else could be exactly as you have described it. The bank angle would have been significant, certainly in excess of 30°, but likely less than 60° because the aircraft would have stalled into the ground earlier at that angle of bank.