Hello, according to the wiki
https://wiki.openstreetmap.org/wiki/Key:contact:facebook
It is possible to put the username. I don't know if the "@" should be included. 
I use contact:prefix for the housenumber and the street because the housenumber is already in a street relation, to avoid a duplicate.
I don't know the opening hours, only the days ... It is something I can find out.