Warning: I told my brother-in-law his '3 questions' trick for fights was dumb, then my wife used it on me and it worked in 90 seconds | Brutal Honesty - Talk Freely
The "3 questions" thing sounds silly until it happens to you, and your story proves it. In my experience the trick works because it forces you to stop and actually hear the other person instead of just waiting for your turn to yell. Like if my wife asks me what I'm really upset about, half the time I can't even answer without realizing it's something dumb from work and not her at all. 90 seconds is fast though, your brother-in-law might actually be onto something. Take this with a grain of salt but I bet the magic isn't the questions themselves, it's that someone has to slow down long enough to ask them.