I'm sorry, MC, but your abilities aren't physics. It's just magic, that you are claiming to be physics. No amount of air pressure, no matter how fast and hard, will cut a wooden block in half. That's impossible physics. And especially not from a few feet away with a swing of your arm, not even if you swing it at 99.999% the speed of light. You'd probably make a nuclear fusion explosion before sending a "air blade" to cut something.
And constructive interference? What the fuck are you talking about? You can't do that with a single wave, unless you have more than one vocal cord. And if you did create a pressure wave with your vocal cord strong enough to blow up an armored beetle, you and your sister would have died as well.
There's quite literally no difference from your powers and magic. They're basically the same thing, because they make no sense, and have not scientific basis for working, and sound arbitrarily made up by the author.
So all I'm saying is that the MC's power is just another form of magic that he likes to call "physics", even though, it's clearly magic. Man, I should probably stop reading this if I can't get over the basic premise of this series and its character.