Mayhem worse? I thought the fight changed after that regardless that sucked mike had nothing in round one but then came back and did great against a gassed Mayhem 
Doubt it had much of an effect.
No.
Mayhem caught him with the crown of his head. I doubt he even felt it. Bisping definitely got the worse of that exchange, taking it right above the eye.
I don't think mayhem ever processed the fumes from the fire extinguishers...