he has passed out after going Nova but doesnt always...even Galactus once said "I underestimated you, your power is far DEADLIER than I imagined" as torch attempted to go Nova in his face....he has also unleashed enough nova flame to "incinerate a hemisphere"...he has taken on and put up a great fight against gravitron, someone i think surpasses magneto in power. Even if Gravitron isnt as powerful,he is still very similar to Magneto. Additionally im not sure how a magnetic field could protect magneto from the torch dramatically increasing or decreasing the general temperature of the environment or magneto's own internal body temperature, ...i think that would be like mags deflecting a powerful psionic attack with magnetism...torch's strategy where he makes many flame copies of himself that demonstrate his same powers, would also make things pretty hard for Mags...however, Magneto is pretty viscious and deadly himself, and wouldnt play around with or underestimate the Torch...I dont know if torch's flame would protect him from magneto using the iron rich hemoglobin in his blood against him...torch is still flesh and blood when he is aflame, but his general physiology is highly different from a regular person...which is why his metabolize such huge quantities of energy and survives 1,000,000+ degree temperature, which is why one could even argue if there is hemoglobin in his blood at all...in my mind it would come down to who tried to kill the other one first.
about the Hulk, he has demonstrated that he can emmit more radiation than a Nuke, at times, but this is highly irregular...under regular conditions he does emmit radiation, but it is not immediately dangerous...that is why his pants r always purple, the radiation changes their color.