Yes, it works just like the prefix-less super: it can be either an adverb or a preposition, and in either role it can be meant physically ("over") or metaphorically ("moreover"). The difference between insuper and super is pretty subtle, but I *think* the former fits better for a more 'static' meaning.

It sucks having to rely on online resources though, that glossary is great for mass references but it's very lacking in proper dictionary entries. My paper dictionary is 2000km away, but tomorrow I'll stop at the library to borrow another.