This has been asked a lot but I am still confused and I'll say why
Let's say that I am playing as Mr. Fixer and I have Jack Handle, Riveting Crane, and Harmony on the field. My friend is Tempest with Localized hurricane out. The Villain is Apostate with three relics out, the Runes of Malediction, and the other two do not modify or redirect damage in any way. I use Strike targeting Tempest, I can see about four ways this plays out.
1) The damage modifiers to Strike all apply, 1 initial, +1 for harmony, +1 for localized hurricane. Fixer would deal 3 damage. As written in the Clarifications and errata PDF, I deal "that much damage" to all non-hero targets and "it doesn't get modified anymore." So I hit each non-hero target for 3, ignoring any reduction or increase in damage. This seems to be the way it reads, but also seems to make some of Fixer's cards like Alternating Tiger claw useless and seems overpowered besides (Fixer targets himself for 1 irreducible damage to everything).
2) The damage modifier to Tempest does not apply as damage is never dealt and the armor modifier from the Runes does. I deal 2 damage to Apostate and all other damage is reduced to 0 by runes. This makes the most sense gameplay wise for purposes of balance
3) The damage boost to Tempest does apply but the Runes reduce it to 1 for the relics. I hit Apostate for 3 and the relics for 1 each
4) Neither damage modifier applies. I hit apostate and all relics for 2.
Basically, I know that source modifiers affect Jack Handle, but do Target modifiers? Jack handle still needs a target and Fixer would damage that target based on the modifiers on that target. And do target modifiers apply when Jack Handle resolves and hits all non-hero targets?