Well.
Kakashi used PS without EMS, maybe becuase of the obitos massive body changes, or maybe because of his mastery of the sharingan.
PS wont make you invincible, itachi doesnt have the chakra reserves to make clones and have all those clones ( even if its one) to go PS, you could argue that he could summon clones and they can summon parts of sasunoo as needed.
Even then i dont think that Itachi could solo everyone.
Madara would probably still wreck him, same for Hashirama. Tobirama and Minato would also probably beable to beat him with a little difficulty. Naruto will def outlast him and has more then enough brute force to break through him and his clones that only have 50% or less of his original chakra amount. Sasuke would probably be able to blitz itachi before more of that goes down, even if that fails he can still put up a decent fight becuase his mastery of the ameretsu and his seemingly high mastery of renngin.