The universe is (as far as we know) far larger than that. The thing is that it's literally impossible for us to interact with the parts of it outside one particular sphere.
Additionally, the universe is not expanding from one point - every point is functionally the "center" of the universe.
I do not understand how it is possible for something to expand without having a central locus. In fact, I am at a loss as to how it is possible for anything that posses bounds to fail to have a singular center. Explain?
Who says the universe has bounds? The classic analogy is of an inflating balloon. If you make two marks on the balloon, they'll expand away from each other, but neither one is the center.
Of course AFAIK there isn't any solid proof for the "finite, unbounded" idea, mostly just speculation. But it was Einstein's thing so we (laymen ;) take it pretty seriously.
Well, Einstein is ;) But yeah, for the sake of the analogy we're talking about a 2-d universe which is the surface of the balloon, nothing else exists.
From all I've read on it (the questionable balloon analogy is easily misleading at first), it's less something you can easily understand and almost something you have to trust. I guess there is another dimension involved and as such it's not all something that can be easily visualised when we're so used to dimensions as we experience them.
Additionally, the universe is not expanding from one point - every point is functionally the "center" of the universe.