I’m guessing…… Den x Hayate? That’s the real OTP, right? (Sorry, my jokes are Chandler from friends level)
2) Which one washes the other’s hair
They probably take turns BUT I’d say Ed is still slightly more into it. He loves to touch Winry’s hair all the time, even when it’s wet.
5) Which one picks in the other’s plate without thinking
Assuming I understood this correctly, I would have to say Ed. It’s shown several times he does love eating, while Winry’s probably the one who even forgets to eat sometimes when she gets very into her work.
9) Which one surprises the other with an adopted puppy or kitten
Ed! Idk, this is just my personal headcanon but after Den dies (nooo), Winry doesn’t really want a new pet (or that’s at least what she thinks because she misses Den). But at that point they already have kids and they insist so ofc Ed gives in. He’s the one who spoils the kids (however in this case, even tho he claims the cat or dog is for the kids, it’s just as much for Winry bc he knows she actually loves it)