No Errata
Q: Can the damage dealt by this Attack action be reduced? (e.g. by Hale Charm or Impervious Delusion?)
A: Yes. These cards reduce the damage dealt, not the Damage characteristic. Enfeeble, on the other hand, does not affect Larval Lance.
Q: Can the Dice characteristic of this Attack action be changed (e.g. by Madness Dart)?
A: No.