i agree that sasuke has more than surpassed itachi, however a couple issues with point you've made. Izanami, we truly cannot speak on fully since it was more or less just created out of thin air as a way to get around kabuto being too OP to defeat...that said, since kishi hasn't given details to the contrary, we can in fact assume that just like tsukoyumi, itachi can inflict it on anyone including sasuke, except that sasuke most likely wont be able to break it easily like he did with itachis tsukoyumi in their battle. I say this because light background on the move stated that it was meant as a disciplinary tech for uchiha who misused their sharingan in battle so if it can be easily broken by them, how was it useful at all? therefore we must asume (until kishi proves otherwise) that it will in fact trap sasuke if itachi can manage to get him in it. As for op, sasuke only ever stays in sharingan form for shorter periods simply because of his usage. He would go ms (or now EMS so its not an issue) and spam susoono and be shooting out ameterasu while doing so, burning massive amounts of chakra (for an uchiha at least, i still say he is around kakashi level on chakra reserves) whereas itachi would enable his ms and use it for nothing more than more accute observation for discerning traps, strategies, and taijutsu...more or less giving him an edge in a fair fight and beyond that he used it for little else but hoping an opponent would look him in the eyes or the ring and boom tsukoyumi, game over. Yes he would use susoono but much more sparingly than sasuke does both because he knows he has low chakra levels, and i also like to think that a tactician like himself would prefer to hold strong techs back until completely necessary, whereas sasuke would spam them left and right as intimidation. Of course, true comparisons cant be made well since it can be argued that if they foght while sasuke has EMS that means itachi ould be edo tensei (immortal) and if it was while itachi was alive, sasuke would stand a better chance (since he more or less beat him before) however i feel that if itachi truly wanted to win he would have easily succeeded in taunting sasuke nito spamming his ms techs more, effectively dropping his chakra levels more, or best case scenario, blinding the eye for whichever tech he overused. Also on your point about izanagi, i believe it was said that all uchiha with ms sharingan could use it, it was simply a very rare use and forbidden because it made you immortal (by turning your death into an illusion for a brief moment) at the risk of that eye going blind temporarily depending on the time length of using it, or if you max out your time, you go blind in the eye used to activate it. Sasuke could learn it if he was taught, its just something that most uchiha (as cocky as a clan can get) would never think they needed to use because by the time many would decide they needed it, they would be seconds from death anyhow.