While we're on the subject of such things, you realize in Texas you are under no oblicgtion to retreat when in your house?
What I posted wasn't/isn't a repudiation of your 'panic room'idea, but information you may not have been aware of......
That's basically just a standing pour but have additional advantages. Those things have interested me for years. Do some more research into energy efficient houses. I don't remember the type construction but recall one very efficient design where the walls could handle a 400 mph wind and required minimal heating/cooling.In Germany when I was stationed there back in 1979 or so, homes were all masonry and had industrial type metal roll up/down shutters on them that were closed at night or when away. Like this:
https://www.innovativeopenings.com/window-security/exterior-rolling-shutters/
I am approaching retirement and will be selling my home and building something away from here with cheaper property taxes. It will be a single story Quad lock ICF home with really thick masonry walls and these kinds of shutters all around. It will also include an interior safe and safe room as well.
https://www.quadlock.com/