There's nothing speculative about where the sun was or it's effect. Yes both pilots would have been heads down, each pilot had different tasks and neither would be able to adequately monitor the others actions or performance in this condition. Neither pilot is likely to have been, lets say polished for this particular exercise. I'm not sure where you get the live engine wasn't developing full power, but it's fair to say if you knew you were going Vmca, pulling the live engine back would be the correct course of action on the part of the flying pilot
I wouldn't argue with a training exercise gone wrong or the benefits of a simulator. I'm not convinced that the exercise commenced at 400 feet, whats the point the takeoff is over, more likely to have been a V1 cut or once the gear is retracted. Nor am I convinced there wasn't an unexpected drag issue from the failed engine. 40 seconds in a level segment with speed decay is a very long time, even for the unpolished.