See my post just above, re: flamefront working to compress the un-ignited air/methane mixture (as the flamefront progresses forward). These ‘ignition’ events aren’t static things (there is forward momentum, and that is imparted to debris and walls as well as the pressure factor) ...
Also, did you see the Philly explosion? What was the wind like that night? 1/2 mile is not that far for debris in wind ...
Most of the information to start the investigation is in the photograph at the beginning of the thread. Notice the house was blown away from the foundation and look at the burn marks in the foundation.