Still about the Izumi x Sasuke thing, based on what you said before:

"do they actually fall for each other or is the situationship a means to an end?maybe to get itachi’s attention.." bro, I believe that Sasuke is just curious and horny, because he is a teenager at the time of the events, Izumi is older and now he sees her as more than an irritant who keeps flirting with his brother. Sasuke doesn't like sharing attention, however, he doesn't intend to stop exploring these new "feelings" towards Izumi. If she didn't tell Itachi, nor hit Sasuke to put him in his place (he just pretends that he never stole a kiss from her and that he doesn't notice her lewd looks, or attempts to accidentally grope parts of her body), then Maybe she's not so averse to the idea. Does she prefer that Sasuke or the brat who picks on her? So it's a type of situationship that could end with Sasuke in love. If you add to this the fact that Itachi is more distant, although he is her boyfriend, it won't be difficult for Izumi to end up involved with Sasuke, perhaps in love. She always has to take the initiative with Itachi or wait a long time; With Sasuke, all it takes is a spark to start a great fire.

"does itachi even ever find out.. what would he think?? would he be jealous?? and bc of izumi or bc of his sweet little brother??" Itachi is perceptive and shrewd, so he realizes something is up. He waits and watches. It's very strange that Sasuke doesn't talk bad about Izumi like he used to, or pick on her for the silliest things. In fact, he always seems to be around when she is. He even points out that Sasuke has matured in this regard, that he is behaving well. Undoubtedly, Sasuke likes him to pay attention to him and praise him for his supposed good behavior, but he doesn't want to be accused of cheating if he's caught. I think a flagrant suits them more than a confrontation. Even if it's harassment or dub-con, because Izumi doesn't want to cheat on Itachi and finds it disgusting to be so intimate with Sasuke (she's in denial, no matter how wet she gets just from the dirty things Sasuke tells her), Itachi wouldn't make a fuss. In fact, he would tell them to keep going; whether it's punishment or because it's so fucking hot to see his brother with his girlfriend. The distant blood relationship, the difference in age and height... Itachi might have fun teaching Sasuke lessons about hypocrisy, selfishness and jealousy, and also how to enjoy the pleasures of a girl's body. Regarding Izumi, he admits that he has been neglectful of her all this time and that allowing Sasuke to indulge himself will also be a gift for her, not exactly a punishment.