Who cooks normally?: If Jaskier wants to eat, Jaskier better cook.
How often do they fight?: Rarely.
What do they do when they're away from each other?: Flirt with other people!
Nicknames for each other?: Eric doesn't do nicknames. Jaskier has a new name for him every time he sees him.
What do they get each other for gifts?: Jaskier likes writing songs about the new sex position Eric has shown him. Eric's gift is not killing him for that.
Who flirts more?: Jaskier, but it's closer.
Do they act different in public and at home?: Nope.
What are little gestures they do for each other?: These are not little gesture people.
Who kills the spiders?: Eric.
Who is "the dominant one" (for however you want to define that)?: Eric.
Who is the cuddler?: Absolutely Jaskier.
What annoying habit does one have that the other hates?: They each have so many.
What do they do to make the other one jealous?: Flirting with other people, but that's both jealousy and foreplay.
What do they do that embarrasses the other one?: Does Eric have to eat people?
What did they nearly break up over?: The eating people thing.
What is "their song"?: Whatever Jaskier wrote.
How do they handle holidays?:Poorly.