#1 - in Texas (at least) you can use deadly force to protect a 3rd party, so personal threat is not required. There is also no requirement to "run away".
No third party was in danger when the gun was unload.
#2 - you don't see what the flamethrower idiot was doing prior to the discharge of the firearm so you can't say as a fact that he was not threatening a 3rd party, you are just ASSuming that as fact.
Irrelevant. What the flamethrower did prior is tied to the previous context, not with the context where the gun was shot in which instance nobody was in danger. Your logic is typical of popo excuse used to kill people all the time.
#3 - As I stated, if someone threatened ME with a flamethrower, they'd get some smaller objects thrown back at them and it would be justified
No object was thrown at the shooter nor anyone else immediately before the lunatic shot his gun.