Who is the big spoon/little spoon?: Seivarden is definitely the little spoon.
What is their favorite non-sexual activity?: Cooking a nice dinner and eating it together. Ignis does the cooking of course, Seivarden help with chopping things.
Who uses all the hot water in the morning?: Neither use excessive amounts of hot water.
What they order from take out?: I'm not sure what Ignis would approve of, but I'm going to go with sushi. If they want to be really really decadent they can eat it with bare hands.
What is the most trivial thing they fight over?: Ignis is very patient but sometimes he gets fed up with Seivarden too self absorbed.
Who does most of the cleaning?: Ignis, although Seivarden does her share too.
Who calls up the super/landlord when the heat's not working?: Ignis tries to beat Seivarden to it because his approach works better.
Who steals the blankets?: Seivarden.
What is their late-night-viewing guilty pleasure?:
Who kissed who first?: Seivarden surprised Ignis.
What would they do if the other one was hurt?: Both would make sure the other one was ok, and defend themselves if needed. They are both happy that they have Radchaai medkits.
Who is more likely to pay for dinner?: They split the bill.
How do they celebrate anniversaries?: Seivarden looks up a really good restaurant and makes a reservation.
What do they name their pet(s)?: There is only Issa. Any other pets get Radchaai names, because they are mostly Seivarden's.
On a scale from tolerable to sickeningly adorable in public, where do they rank?: Towards tolearable.
Who cooks normally?: IGNIS. But Seivarden helps.
How often do they fight?: Not that often. Ignis is patient.
What do they do when they're away from each other?: They usually work and keep in touch with other friends.
Nicknames for each other?: Neither are really nickname people.
What do they get each other for gifts?: Seivarden buys Ignis fancy coffee, Or tea or other food specialities if she's been in the Radch. Ignis gets her tea and gloves.
Who flirts more?: Seivarden.
Do they act different in public and at home?: Not really.
What are little gestures they do for each other?: Seivarden does the washing up after Ignis has been cooking. Ignis makes Seivarden nice breakfasts.
Who kills the spiders?: Either of them, although they aren't really bothered by spiders.
Who is "the dominant one" (for however you want to define that)?: Probably Ignis, in that he is the less emotionally dependent one.
Who is the cuddler?: Seivarden
What annoying habit does one have that the other hates?: Seivarden can annoy Ignis by sometimes expressing Radchaai prejudice, Ignis can annoy Seivarden by being too distant.
What do they do to make the other one jealous?: Neither of them are particularly jealous.
What do they do that embarrasses the other one?: Seivarden can embarrass Ignis by expressing Radchaai prejudice. Ignis very rarely makes Seivarden embarrassed.
What did they nearly break up over?: Seivarden accidentally said something rude to one of Ignis' friends. She apologised.
What is "their song"?: I have no idea
How do they handle holidays?: They celebrate the holidays they find relevant, for social reasons.