I don't know, I'm afraid, whether pronouns were used to express status relationships. I have never understood that they were, in Classical Rome. There was not, so far as I know, any equivalent of the French practice of using the second person plural for "superiors", or the Italian practice of using the third person, or for that matter the English practice of the "Royal we".
I would guess -- but I stress it is only guesswork -- that such practices are very likely a post-classical development. For example, I had always understood that gladiators would greet the giver of the games with the tag "nos morituri te salutamus" ("we who are about to die salute you") where "te" is the second person singular. This must be about as extreme a power imbalance as one can find: a bunch of slaves who are about to die for the pleasurable advantage of a grandee. Yet, if my recollection is right, the pronoun is commonplace. But I am not sure how we know, and I could easily be wrong.
Names certainly did express status -- for instance, through adoption or the relationship between the former master and his ex-slaves, whose names would often reflect their patronal relationship. Changes or adoptions of name ("Pompeius Magnus", "Augustus") strongly expressed status. But how far this was reflected in ordinary colloquial discussion, I do not know. The best place to look might be in drama or in letter-writing.
So far as the infinitive is concerned, there were formal and poetic infinitives (for instance the infinitive in -to). But so far as I know their use was determined by the formality of the context (e.g. legal or religious) rather than the relative status of the orderer and the ordered.
I'm not sure I agree with mrcolj that "Rome did not have a high maintenance culture", nor that people were "casual". I suspect they were the very opposite of casual: there was a high degree of formality reflecting power relationships, both legally (e.g. the institution of slavery, and of "potestas" within a family) and factually, e.g. through the relationship of "patron and client". There are plenty of pictures of this sort of relationship in "low" literature (e.g., Juvenal Satire I has a nice, though presumably over-stated, picture, and there is much more in the Satyricon), and considerable evidence that it had distinctly "formal" features, in terms of a complex set of mutual expectations about how each side would behave. Roman culture simply oozes with devices to mark out legal and political status: in terms of retinue (e.g. lictors accompanying magistrates), name, dress (the toga praetexta etc), appearance (wreaths of different materials depending on whether it was a triumph or an ovation being celebrated) furniture (particular chairs and so forth), and a whole parallel set of expecatations and devices to mark out wealth, which is a slightly different matter. It would not be at all surprising to find this marked by grammatical difference too, but so far as I know it was not. Yet one must be careful to note how slight and skewed is the evidence available to us.