Hulk has been in space without gear (well, he had respirator), that's pretty damn good resistance to cold considering that he showed no ill effects. Also, Torch can't keep nova up forever. Maybe he has enough time to destroy Hulk, maybe not.
He has a damn good resistance to cold. Iceman's power level has changed so much during the years and there definitely are some versions that couldn't even scratch the Hulk, don't you think?
Your scenario depends on various factors. Firstly, Human Torch would be burning Iceman too while doing his nova flame and I'm pretty sure that Hulk resists heat better than Iceman.
Secondly, Hulk has proven to have huge resistance to cold and a healing factor that's along the best in the Marvel Universe. Really, Hulk could deal with the punishment that Iceman deals. I might be wrong since I don't know Iceman's current power level. It's one of my problems, can't afford to buy every comic.
Thirdly, if Torch cannot destroy Hulk with one try he's gone. And since he has to watch out for Iceman in your scenario he will have serious troubles damaging Hulk without burning Iceman a new one.
Johnny goes hotter than a Nuclear Explosion. And its not a matter of whether he survives it, but he will be flayed to his skeleton. And iceman can exist as water molecules.
Hulks body has to go through the process of growth such as muscles, viens, tissue etc. Iceman takes the moisture from the air and forms. He cuts out all the other stuff cause hes just ice.
Back when X-Factor fought Hulk, Iceman froze him so cold that he wasnt able to get angry enough to break out. Although it was grey Hulk, it was still ice-coated Iceman, and the same "get madder, get stronger" rule applied.
Iceman could just freeze the bloodflow to the brain and revert him back to Banner.