Yes, you are exactly correct. It refers to the support of the community.
I think, technically, there should be a comma:
It is amazing, the support we get from the community.
Similarly, you could say:
The support we get from the community, it is amazing.
Also common, and perhaps even preferable:
It is amazing -- the support we get from the community.
The support we get from the community -- it is amazing.
(This is a nice page on how to use the emdash: http://www.thepunctuationguide.com/em-dash.html)
In all these cases, the support we get from the community describes it. These examples are typical of spoken and informal usage. In formal usage, the "it" would be considered redundant and therefore incorrect. I don't think there's a particular term to describe this kind of sentence construction. It's very typical in speech patterns. People say a pronoun, and then clarify the meaning of the pronoun. For example, you would use this kind of construction often if you were writing dialogue for a novel. It suggests to the listener/reader that this is a realistic representation of how that person speaks.