If Itachi was confident to defeat Madara he would do that instead of stopping Kabuto i believe.
Anyway, i say no, Madara may have no counter to izanami but i'm sure he knows abt it. He's got rinnegan, EMS, Mokuton, plus i'm not really sure if Izanami would even work on him. I mean Madara doesn't seem confused, i think his mind is strongly set on his goal, i don't think he hesitates or he tries to defy who he is or anything like this. Well but i can't be sure abt that. Still i'm sure Itachi wouldn't be able to solo madara. Maybe Madara when he was alive, i think of them as of kinda equals. Edo Madara is on a whole other level.