sorry if this is late, but off the top of my head i can think of bits and pieces.
inf.I.ii "mi ritrovai per una selva oscura" - i have a feeling that selva oscura is some sort of figura etymologica of something that appears in the dido encounter.
that's just some linguistic silliness though.
i don't think vigril is made out to be christian - that's why he's actually in inferno, i.e. he can't be in heaven/paradiso because he isn't a christian. it's not all bad though, because dante cleverly places him that the top of hell in a place called limbo (the further down you go, the worse you are). this is basically a place for all sorts of people, particularly those who were around before christ even existed - such as virgil. obviously it would seem unfair to have them in the very depths of hell as they were unable to avoid their lack of christianity; yet, morally, it would be unfair for dante to put them anywhere near heaven. interesting one.
edit - i thought so about the linguistic thing quite rightly:
errabat silva in magna; quam Troius heros
ut primum iuxta stetit adgnovitque per umbras
obscuram, qualem primo qui surgere mense. in my opinion, although i think there might be more than one shaded grove in this section, this one is the most memorable. although i think that there might be other silvae this is, i believe, where dante finds that phrase (perhans subconsciously unintentionally) selva oscura.