If you can think of a ship, i will answer these questions for them
who cooks normally?: Steve. Definitely Steve. Unless the taste of burnt lasagna is something you enjoy, Steve keeps Tony out of his kitchen.
how often do they fight?: How often don’t they fight?
what do they do when they’re away from each other?: Video calls, phone calls, text messages (of all sorts) they rarely sever contact, Tony gets called out a lot in meetings for being on his phone.
nicknames for each other?:There is always the usual pet names of ‘baby’ and ‘honey’ but Steve has one really emasculating name like Tonycake or Tonypie, that Tony pretends to hate but secretly adores and he ‘retaliates’ with ‘Spangles’ or ‘Capcake’ which make Steve blush and he pretends to be irritated by but secretly loves as well..
who is more likely to pay for dinner?: Real talk, Tony probably pays for everything before they even get to the restaurant.
who steals the covers at night?: Steve probably because he swears that Tony keeps the tower at arctic levels, but Tony doesn’t mind, because Steve steals him at night too, pulling Tony closer to leach his body heat.
what would they get each other for gifts?: Tony makes attempts to be romantic with flowers and chocolates (and apology blow jobs are definitely a thing) Steve tried buying him electronics once and then decided to stick to flowers, alcohol and evenings alone.
who remembers things?: Steve and Jarvis.
who cusses more?: Tony Tony Tony Tony
what would they do if the other one was hurt?: Steve would mother hen Tony with or against his will. Tony would threaten to/actually destroy who ever had hurt his Steeb.
who kissed who first?: Tony kissed Steve first and Steve blushed and hesitantly returned the kiss.
who made the first move?: Tony. Steve’s too shy and nervous for his own good, used to living in a world where a man and another man isn’t something that’s widely accepted if at all.
who started the relationship?: Steve decided he needed consistency. And he eased Tony into the commitment.