1. who cooks normally?:
I'd say they split this one evenly. Maybe even do Awesome Team Combo cooking together. That being said, I also imagine these two'd eat out a lot. Dude Mac there's this sushi place RIGHT IN FDC and the chefs are all Lickitungs you gotta check it out, etc.

    2. how often do they fight?:
Not very often, as far as serious fights go. Lots of playful teasing and bickering, though, because that's just how they roll. I imagine if it was a really serious topic, they'd be able to work it out pretty smoothly.

    3. what do they do when they’re away from each other?:
Lots and lots of training. Mac probably has Lyra's pokegear number by now, so they could also probably annoy each other with messages about top percentage rattatas etc.

    4. nicknames for each other?:
They don't have any for each other in canon, but I could very easily see their banter giving birth to some kind of cutesy nicknames that make absolutely no sense to any outside parties.

    5. who is more likely to pay for dinner?:
They'd split the check. Or take turns. It's cool, Lyra has an Amulet Coin, she's not that strapped for cash or anything.

    6. who steals the covers at night?:
Lyra (and/or her pile of six-foot monsters) would probably end up unintentionally blanket hogging, but if Mac was cold then that would be swiftly rectified with cuddles. All of the cuddles.

    7. what would they get each other for gifts?:
I imagine they'd both be pretty okay gift-givers, though Lyra might end up giving a really awful gift with good intentions behind it every once in a while, because she's a special kind of dense.

And, of course, every so often they'd give each other incredibly dumb gag-gifts just because.

    8. who kissed who first?:
Lyra, probably. She's pretty impulsive by nature.

    9. who made the first move?:
This one's up for grabs, though. I think they'd both be equally likely. Maybe a bit more likely for Lyra, given Mac's tendency toward obliviousness, though.

    10. who remembers things?:
Mac, most likely. He's such a sweetie. :')

    11. who started the relationship?:
This one'd also go to Lyra, I suspect. She'd feel like there'd have to be some kind of official gesture of it and try to daydream scenarios like a romantic confession out in the rain, but in actual execution, it'd probably be a clumsy blushing fumble in the middle of casually watching TV or something.

    12. who cusses more?:
Neither of them are really potty-mouths.

    13. what would they do if the other one was hurt?:
Finally, a pair where I can give an answer that's not "these guys are bad at comfort." Mac and Lyra'd be awesome at it. Boss-tier comforters. If Mac got sick or beat up in a match or something he'd have Nurse Lyra at his side in a heartbeat, bearing bandaids/dayquil and cookies (slightly under-baked, but at least they're edible). Likewise, Mac's the kind of guy who's got your back. Same story for emotional pain: they'd both be the textbook definition of supportive.