[X] Fire through Abby, quite probably killing her, to kill the Fiddler. Plus, she's part of his ritual, without her...well. If it can kill him, maybe it's worth it? And more than that, what if she wants it. It might be the way to solve this.
I choose this option for two reasons:
(1). It is very much in character for Stoneguts.
Gabriella was already clearly unready for this and skeptical: when she'd been told the plan, she'd objected to the tune of concern for Abby.
And Stoneguts knew that if Cora was here, well--
She'd want to save Jason "Smiles" and not merely because of her son's attachment. And King Stoneguts had made the decision, right here and now where his monarch for the season was unable to see it, that killing the Fiddler mattered more.
Once he was dead, the pair could hopefully be retrieved, but if need be, risking them…
More coldness. And it was that same cold place that told him that if it wasn't for her status as a Wizard, he'd leave Gabriella behind.
But...if he had to face Cora…
He'd regret it and that wouldn't stop him from acting.
(2). I'm fast becoming sick of the Fiddler. He is good tool for and means to antagonsim, but he isn't a very effective antagonist.
He, his powers and his plans are all grandiose, but vague in a way that tends to drag after a while. He is not a direct threat to any Changeling (that is named/that matters) and as an indirect threat he seems to act mostly as a purveyor of the narrative equivalent of side-quests/mini-boss quests.
Also...I didn't think I needed to say it, but the Fiddler isn't a Fae. I mean, it's been pointed out by people several times before, but nope. He is not a Fae, True or Otherwise. He's a weird demon-spirit-thing of some kind, in that vaguely fuzzy Dresden Files category of 'Demon/Spirit/???'.
Most DF spirits tend to be very limited in their capacity and inclination to interact with and galavant about the mortal world without restriction.
Aside from the various types of vampires (spirits sharing and/or possessing human and/or once human flesh) and faeries (who amongst the spirits of the Nevernever are rather unique in their relationship with the mortal world), there aren't many spirits from the Nevernever who can freely machinate and carry out their machinations upon earth to the almost human degree that the Fiddler can.
So not unheard of, but still rare.
On a side note, I can't help but notice that DF faeries are bit like WoD werewolves.
However where a werewolf is a mortal that is part spirit, a faerie is spirit that is closely tied to the mortal world.
That is to say that faeries are a bit more 'physical' than most spirits (such that their bodies don't immediately start to dissolve into ectoplasm when they are killed on earth) and can survive quite well in both the Nevernever and mortal worlds (though the ubiquity of iron in modern society has made the civilised parts of earth that bit more uncomfortable for them).
I wonder if werewolves can (like DF faeries) hunt and feed within the Nevenever and still be free to return to and eat on earth as well, without risking dying from the ectoplasmic nutrition that their bodies taken in and used destabilising.
