1) compared to the energy of the collapsing building, it will just be a puff of dust. Nothing to worry about.
2) and this would be different from any other fire? Burst disks pop, vents in a hiss, some near by wood will burn slightly faster, problem will solve itself before any first responders get to the scene. Nothing to sorry about. Ever seen a burst disk pop? Loud for a couple of minutes and done.
3) 1 of a million hazards. Hitting a propane tank would be a bigger worry. Some ordinary household cleaners getting mixed together would be a bigger worry.
Many years ago there was a huge flood in Colorado. Washed though a welding supply company. Hundreds of welding bottles (many oxygen) were washed down stream. The locals know about it (old co-worker was there). One of those quick mountain flash floods. Decades later they are still finding filled bottles that rattled down a river bed, filled, and being used by the local farmers who find them.
Yes, there is a lot of energy in a filled scuba tank. but they are not that bad.