Yes, backbone is used correctly, but in the first sentence, the phrase " it's need" doesn't make sense. Do you mean 'it needs to be realized?" or perhaps, it must be recognized etc.etc.etc.
In the final line, 'One of the causes is the very minimal existing digital library facilities' is a sentence fragment.
This would read better if you said, something like " In order to service the needs of the entire campus community, the present minimal digital library facilities must be greatly expanded."
yes, but the line "Again, it's need to be..." doesn't make sense. The kind of it's you used is a conjunction for "it is". I think it should read, "Again, it needs to be..."
Well a backbone is used to support and help us stand and do things. So in this sentence you are stating that a library supports an education and research institution.
i would say so, yeah. makes sense cuz a backbone is the supporter
yes it is
it is used as a metaphor meaning supporting something