Hasn't "Another correct answer" sometimes had "building" for "hale"?
'Ae, hale is not just house. It can be building in general, like how they say Honolulu Hale for city hall.
Is it usually qualified if it is other than a house? Like your example Honolulu Hale, or like hale kū'ai?
Often but not always. Technically, the answer to this prompt could legitimately be He is inside the building.
Why do you have to say "aia 'o ia" and not just "o ia"?
Aia signals location.