Wow, Tavern, what a pregnant find. A number of thoughts arise to me, and no doubt to others, and probably more will arise as we digest this.
1) Perhaps most importantly, because we want most to find the origins of these people, is who was Elizabeth Halpin and who was her husband??? If we (you!) could find deeds to do with her husband's death or her inheritance of the Bridge, that would be a quantum leap back a generation.
2) Why did Frederick have to buy out the estate? In 1856, Anne Halpin had more than enough sons established in professions or at sea to be able to afford to not see the whole family go bankrupt. For my part, I feel sure that George in Dublin would have helped. So why Frederick, who we are told by the burial inscription, was James' nephew? And why did he leave the hotel (and his entire estate?) to Fanny and Louisa, and to no others?
3) Frederick, as a sea captain, may have been based in Kingstown, a deep sea port. I am sure it is mere coincidence but it needs to be recorded that there was another Fredrick Halpin in Kingstown at the same time, Frederick James Halpin, youngest brother of the Rev NJ Halpin, who conducted a private school there.
Most grateful for this excellent research, Tavern. Please keep it up as long as you can. I suppose that you are adding these details to that excellent online project you advised of earlier (put together by an Aussie, it seems).