SpoilerSuperior effect die on your part reduces the D8 physical stress you would have received from the boomerang to d6. No on fire complication.
Now to deal with katana violence: 1d8 buddy, Hot Tempered d4 (add a d6 to Doom pool), Enhanced durability d8=
1d8+1d4+1d8 → [6,3,3] = (12)
9 with a d8 effect. That would hurt but...SFX invulnerable, eating up the die I just added to the Doompool.
Doom pool is 3d6+1d8+1d10+1d12.