Latin doesn't really allow for the social distinctions that we make in English. Modern translators are obliged to deal with (indeed, to agonise over) this very problem, for which there seems to be no perfect, or even an agreed solution. It's the same for other modes of address. As long as there is consistency and no ambiguity, the choice is that of the translator, which seldom seems to be criticised.
Peter Needham, in his Latin versions of J.K. Rowling's Harry Potter stories, uses Dominus and Domina for Mr. and Mrs. Dursley. At Hogwarts, the staff are variously professor, magister, magistra and so on, while Harry is himself formally addressed as Domine Potter. All Needham's usages are well thought out and quite acceptable.
In Superbia et Odium I myself used honestus and honestior to indicate the different social classes of, say, Mr. Bennett (a country squire) and Mr. Darcy (a wealthy man with a position in society). Mrs. Bennett is matrona, which allowed dominus and domina to be reserved for members of the aristocracy. For a knight of the realm I used senior, but if it is necessary to address a man as 'Sir', then O mi Bone, Bone Vir or Optime Vir indicate different levels of familiarity or respect.
I can't think that you have any need to strain for an accuracy that may not be genuinely attainable — just use whatever seems to fit comfortably with the social and professional situations of the speakers, allow the context to help you where appropriate (e.g. to choose beteween magister and dominus) and try always to be consistent.