I would also like to know the correct spelling of this word. Both options, with and without a space, are probably correct. I trust this source: wehewehe.org. A separate spelling is given here. But in the video lesson 'Ka Leo ʻŌiwi', Episode 2, 10:57, I found 'makuakāne', no space mark. However, I've seen an inaccuracy in those videos, like Poʻakahi and other days of the week without kahakō (vs. wehewehe). Altough I have doubts about it too because of 'Po'ahia'. Where is the Truth?
Just keep it spaced. Sometimes you'll so 'oia or 'o ia. A lot of words are compounds of words. Like 'wai'. It's everywhere because water is everywhere in Hawai'i.
You'd have to ask a Hawaiian language teacher about makuahine. My guess is it is a slang that happened because of the double wa sound in makua wahine.
"No hea" is actually asking for a person's origin, not their location. Literally, the prompt is asking "Where is your father originally from." "Aia i hea" asks about a person's physical location.