Why is demon-Freddy so mortal at the end?

Especially considering how we had just seen how he could increase in size to cover the horizon, and in the end he gets stabbed with a kitchen knife - and limps. His elongated tongue also gets stabbed, which causes him much consternation. And finally Heather and her kid trap and incinerate Demon-Freddy in the furnace - the furnace in the dream-sequence Demon-Freddy made himself. So why is he so vulnerable all of a sudden? Seems like anyone equipped with kitchen utensils would stand a decent fighting chance.