"The building is over here."
Actually do we say Over Here in English?
Anyway, because こちら is used, the building should be around the place the speaker is.
If it is not that building or this building but just the building, should it not just be totemono, instead of sono totemono?
It depends very much on the context, and if an emphasis is needed. Anyway it is not quite common to always mention この, その. I agree with you that it should be just たてもの whenever it is allowed. However we cannot tell from just an isolated sentence.
Why not just "here"? It's a bit frustrating that the app is so strict... this isn't math where everything is either completely right or wrong.
is その really necessary? if left off wouldn't the listener just assume " the store" anyways?