i totally agree with the "make up before going to bed" rule. they'd probably figure that out pretty early on, but imo through mike's argument with somebody else. as in: will would share that piece of advice with him and they'd automatically know to apply it to their relationship as well.

as for the last part, i do definitely believe mike would be more comfortable with his sexuality and himself in their relationship, but nothing is ever black and white for me so i feel that there'd still be some lingering internalized homophobia for a while. he'd need to adjust to being out of hawkins and in a more accepting city (i always picture them in nyc personally), but the bit that sticks can lead to dark places.

i think he might get grumpy sometimes, go quiet and know that it's irrational, which makes him more upset. it would hurt will because mike isn't providing a reason for it; he just went silent and frowny halfway through the day, all because he's fighting with himself inside his head. internalized homophobia is a pain to ignore and is incredibly bothersome to deal with. but that's just how i'd see it affecting him/their relationship

that's in regards to mike specifically. i do think it'd be a different situation for will