How should he be addressed? At the moment the guy's name is Iosif Vasil'yevich Khilnoff, and I know about the Slavic practice of calling men by both their given name and patronymic, but I don't know what the equivalent of "my lord" would be, or indeed whether a boyar had any particular mode of formal address. (Obviously this might vary depending on the language -- lots of Eastern European aristocracies had boyars -- but since this isn't set in the real world, I have some wiggle room as to the specifics.)
Also, are there any other details of protocol that people happen to know, regarding how to show respect to an aristocrat of that sort? Bowing vs. kneeling, etc. The visiting protagonists are foreign gentry, plus one earl, but they'll also have local peasants with them.
Search terms include "address for a boyar," "boyar mode of address," etc, with no luck. (Largely because it's also a last name. I suspect I'd do better if I could search in, say, Russian, but alas, that isn't one of the languages I've studied.)