Yeah, with Murphy more distrustful of him, and Mab keeping Molly away (it's probably better for Molly to keep out of a Denarian experience anyway), I think Thomas is Harry's best choice. Relapsed White Court or not, both Harry and Thomas place a huge value on family, and still mostly trust each other. Though Harry did try to steal Thomas's boat.

Mab has a better health plan than Butters, and Butters would be easier to kill. Harry doesn't want Mab anywhere near Bob (neither does Bob for that matter). Perhaps Sanya, it'd be a perfect chance for Harry to get the third sword. () But having Sanya along would sow even more distrust from the Denarians, and we want to avoid as much backstabbing as possible.

Thomas is the best choice.