Thanks so much for that information, Andrew! I did some research on the names you supplied, and there is a hotel in Paris called the Hotel d'Albe, but judging from its website, I think it looks too modern to be the same one where JMB stayed. I'm not sure. I also found several sources saying that the Theatre du Vaudeville's original building still exists, but it has been a Paramount Cinema since the 1902s.
I will be making a day trip into Paris tomorrow, but I think my friends will drag me to see the non-JMB-related parts of the city, so I will have to investigate this another time.
I have also been trying to find out whether the L'Hostellerie de Guillaume le Conquérant in Dives-sur-Mer still exists. I have seen some modern photos of a building that greatly resembles the one in the photos of JMB, Sylvia, and Michael playing Romeo and Juliet, but I couldn't figure out if it was the same building or not. One of the many occasions where a better grasp of French would have been extremely useful!