But then you run into the plausibility of the story itself. So I am to believe that he was able to stay calm enough to be able shoot around his own daughter and hit only the bad guy, while his wife missed completely (both felt the urge to shoot simultaneously?). Even trained soldiers can't pull this shit off, never mind a father when his daughter life is at stake. I'm sorry but that can't be the true story. Maybe elements of this are true, but something has to be amiss.
Without diagrams or whatnot, nobody really knows how much of a target the intruder was presenting and how much of that target, if any, the daughter was occluding. The guy made it into the lounge room, which could suggest that the father shot him from the side or at an angle with the daughter in front of the intruder, presenting little risk to the daughter from the father. Conjecture, but it's plausible and the most likely scenario if the given account is factual.
If you've ever watched some kind of practical shooting comp, you'll see plenty of people regularly doing this at a range 20 feet, let alone 3 feet. You have no idea how much practice the father may have had.
As for the mother, the father may have told the mother to shoot at the other guy, she may have been at a trickier angle, she may have been a crap shot, she may have been more concerned with not-hitting her daughter, she may have fired to suppress or intimidate or she may have flinched and accidentally discharged when the father started shooting. Anything is possible.
You're doubting a story because it fits your view. It's ok to be cynical of the media, but you're flat out wrong about the plausibility of the story.