"Where's your house?"
It's the same, 哪儿 is common in CHina , but in Taiwan we always say Nali.
Correct! I always remember 哪里 as "where" because the mouth radical on the left (口) and the 3rd tone makes it kinda seem like a question, whereas 那里 or "there" with the 4th tone sounds more definitive.. Not sure if this will help anyone
吗 is basically used for closed questions that require a "yes or no" answer. 你累了吗, Are you tired? 你喜欢吗, Do you like it?
We wouldn't use 吗 if asking about time and place as open ended questions as the answer could be 那里, over there; or 明天早上, tomorrow morning. Unless of course you asked something like 妈妈在这里吗, Is mom here? (again this is a yes/no question even though its related to a place).
I guess you don't need it because you have "where" as the interrogative indicator.
The translation is more directly "Where is your home", not "where is your house". Common usage probably makes the two interchangeable, like how Spanish lessons separate "hogar" and "casa". The distinction is similar here.