I suspect Dottie already knows where everyone is. Have you noticed everyone who matters already knows everything about Hugo and Stoker when they meet them?
As to the black card, would you sell an endless stack of signed blank checks?
We finally get to the practicalities of being a couple. It's only doable by remaining anachronauts.
What will Dottie demand in the future for the limitless credit of the black card?
As the saying goes, still waters run deep. We, and Hugo get a new appreciation of Stoker's true depth. We also get a disturbing glimpse behind the benign masks some of the major players wear. Hugo will never trust surface impressions again.
In the early chapters Graeme said it had been many years since he lost his squire. There must be a deeper reason than being far from home he hasn't gotten another.
Perhaps it's also linked to why he doesn't remove his helmet and shuns his own image.