No it's not unless you can provide a better translation than the one you provided. Feitan makes two references to pain. Phinx comment only means Feitan uses it when he is pissed, not that being pissed is the requirement. If that is how you want to interpret the Hatsu fine but it makes no sense from a narrative point of view to work that way.
No shit. That is not a special property of pain packer. That is called suffering the effects of intense heat, lack of heat resistance. The rest of that is just baseless conjecture. Attacks in manga usually go away when the enemy goes dies. Doesn't mean it would stay until the enemy died unless specially mentioned to work that way. For all you know an enemy with enough heat resistance could endure the sun until it ran out. Stop making up conditions and hatsu not hinted at in the manga. The fuel comment was also about his sun not Zazan.