Since a chance has been given to him, Eric found it best to train his Fire Controlling abilities now. He has free time, and it is best if he trains as much as possible because regardless of the 15 months of experience, he still hasn't escaped his Expert (Level 4) title in Fire Manipulating/Controlling.
But also, becoming better and better in Fire Controlling will inevitably help him obliterate what little Inner Demon is left on him, and learn Lava Controlling better and faster. A mind that is transparent can pick up more wisdom after all.
Here, he has a big advantage in terms of becoming a better Fire Controller. A Grand Master in this power is to his disposal, King Michael has become his temporary Mentor here once more and will inevitably prove useful to forming Eric in to a stronger Fire Controller at least.