For the Fire Wolf: In reference to Skoll, the wolf from Norse mythology who chased the sun across the skies, I thought I'd use variations of the name skoll, starting with the first evolution, mixing skoll and puppy, making Skollpy.
For the second evolution I thought of an already formed and ferocious wolf using the mixture between Skoll and atrox which is ferocious in Latin, thus becoming Skollatrox.
For the third evolution (would it be the last?) I thought of a kind of strong, fierce and flaming fire wolf walking on 2 legs with limbs that allow it to fight as well as release fire and the name would be WereSkoll.

Skollpy->Skollatrox->WereSkoll