"A von" certainly is a cultural allusion to high social status. German surnames with "von" are, or at least sound, aristocratic, just like Spanish ones with "de"; in both cases, people have sometimes adopted a "von" or "de" to which they are not entitled in order to make themselves sound more patrician.
http://es.wikipedia.org/wiki/Von

I think "un von" just about works in Spanish; I think it might help to put "von" in inverted commas. I hope so, because if not, it's going to need reworking, and will almost certainly become clunky and heavy-handed ("cuyo apellido empezaba por von", or something).

"If you please" can suggest surprise or anger:

"if you please
•formal used to express surprise and anger
They want £200, if you please, just to replace a couple of broken windows!"
http://dictionary.cambridge.org/dictionary/british/please_2

Here it really means the same as "no less", and "nada menos" captures the tone quite well, I think.