This name has always struck me as very "dorky", but that might just be because I associate it with Ferguson, the annoyingly geeky brother on
Clarissa Explains It All (wow, I haven't thought about that show in ages!). I think, however, I could become inured to it if I met someone by this name who wasn't consistent with my current stereotype, and I could possibly come to like it.
I think
Gus makes a fine nn. I like it better than something like Fergy.I also think it fits in well with your other choices.
Fergus Oliver is ok, but I think
Oliver Fergus sounds better.