To be honest Itachi doesn't need to stray from his 3T arsenal too much in this fight. Using MS techniques just exhaust his chakra (as we saw with Sasuke) and Itachi is much smarter + he won't be bloodlusted and use his most powerful techs like Sasuke did.
Danzo already showed he can be tricked momentarily by genjutsu; Dusk Crow, finger genjutsu, or any other 3T genjutsu is enough to immobilize Danzo for a moment, followed by shuriken or a kunai to the neck.
Danzo already was killed one time by mere shuriken. Itachi, being one of the best shurikenjutsu users, will be successful in killing him a number of times this way.
Baku gets taken out by Grand Fireball Jutsu/Amaterasu or gets sealed with Totsuka. Or Itachi controls it with genjutsu.
Ribcage Susano'o can be utilized if must for quick defense against Danzo's wind attacks.
Izanami = hard counter to izanagi.
How can Itachi counter Jūinjutsu in CQC ?
He avoids close combat.