It woud have been helpful if he had said WHAT SOLVENTS he ws using. For example, was he using Ed's Red, with it s acetone component. Was he using white gas (camp stove fuel)? And, it seems a little strange that he would use enough to cause a rag-bin fire. Was he cleaning an artillary piece, or what?
It also seems strange that he was standing outside a door and was not injured, while his wife was outside and was injured. How did the explosion move a concrete slab and not blow the door out on him? Also, how did the explosion push flames through the dirt/concrete sufficiently to set his wife's har on fire without buring down the house?
To me, this still sounds like a gas explosion. It might have been gas from evaporated solvents, rather than something like a propane leak. But, it seems like the gas made it out of the room before it exploded, so that not all the force was created inside the room. Perhaps fumes moved into other areas until they found an ignition source, then ignited and created pressure and flames in multiple places. Still would seem to have required a LOT more solvent than I would expect to have been used to clean a gun. Maybe he had a spill and cleaned it up with rags, leaving them in the room?