Should 'The stadium is here' be considered correct?
Yeah and that would be in my opinion the best translation
Am I right thinking that the difference between täälla/tuolla vs tässä/tuossa is that the former is equivalent to here/there in a general sense, not implying specific location, while the latter is here/there indicating the precise location?
Yeah. Also, täällä/tuolla is usually further away from the listener, whereas tässä/tuossa are close to them.