1. In your dictionary (you should have a print version but the great Lewis and Short is online http://www.perseus.org/cgi-bin/resolveform) the verb “vulgo” means
what?

I don't know about the verb, because Lewis and S. only gives nouns, but it has to have something to do with lots of grubby common people. Right? and an o on the end can mean things like ablatives and datives right? Hmm...still no verb form. Hmph.

2. If the form “vulgata” means “having been made _______”, and if what I said
above about Greecisms, Hebraisms, and inelegant things is true, (which it is), then
what conclusion can we make about Roman Christian society in the late 4th century?

That they weren't really our sort.