He wasn't going insane. If this green fire really had such an impact on his dragon breath, then it would have the same effect over the other dragons as well.
So why not use this calamity to the best benefit then?
Plus he started to have a vague clue about the origin of this green fire. Despite it being something unbelievable, he couldn't deny his feelings now.
When the green fire came in contact with him, he felt the same feeling he had when he was upgrading his dragonair power. This green fire had the same nature of the power of the trials he went through, like it was made by the same force or something.
He still didn't know how, but this was something he was totally sure of. This green fire might be the nemesis of the purple fire, but the best thing to evolve any dragon, including himself.
