Believability is not based entirely upon emotion, imo. I am basing it upon common sense. If I hear scary noises in the middle of the night, the FIRST thing I do is check where my husband and kids are, to make sure it is not them making the noise. That is basic common sense, not emotion based.
And IF I accidentally began shooting one of my family members, I assume they would begin screaming out in pain and fear, and would not be totally silent, as OP would like us to believe. Again, common sense, not emotionally based, imo.
I don't have to believe with certainty that they fought loudly that night, to believe he is lying when he gives us that ridiculous story of phantom intruders.It could have happened differently. Maybe she went to use the bathroom and he grabbed her cell, to see who was texting her? And he saw something that angered him and went after her?