There are multiple scans stating that Tsukuyome is instant.
Itachi states that only a blood relative (Sasuke) can break his Tsukuyome.
MS Sasuke caught Bee in a much weaker genjutsu for 2-3 seconds.
Edo-Itachi caught Bee in a much weaker genjutsu for 1-2 seconds.
Naruto warns Bee to avoid eye contact with Itachi because Tsukuyome will neg diff him.
Yagura was put under genjutsu for years.
Conclusion: Itachi can neg perfect jinchurikis with Tsukuyome (as long as he establishes eye contact).
Instant in real time, not in the genjutsu. A Perfect Jin have 2 minds connected and their chakra are connected. Itachi have to have his chakra go to his victims brain to affect their senses such as time perception but as I already said, Perfect Jins are connected in mind and chakra so the Bijuu would be in the same time perception as their host.
He said only someone with his blood could defeat him, only a true Uchiha. He said that to Kakashi who was trying to use the Sharingan to fight him so all he said was Kakashi can't fight him as a true Uchiha could. Genjutsus all share the same weaknesses, they all work the same (their chakra affecting the victims senses via brain).
Real time gets real time results. In Tsukuyomi, Bee would be snapped out in the same time but in Tsukuyomi time so it would still be instant in real time. (For both Sasuke and Edo Itachi comment)
Naruto wasn't a perfect Jin at that time nor have Bee been shown telling Naruto that the Bijuu can snapped them out of genjutsus.
Do you know how? Do you know if Yagura was even a perfect Jin at that point or if he even had the Bijuu in him? All we know is that Obito controlled him for a time but if Yagaura had the 3 tails in him then why didn't Obito have it? Why did he have to go after it with Deidara many years later? If you can't answer those questions then don't use examples that we have no info on.
Your conclusion is wrong since your points are wrong. Sure I don't have manga scans to show my responses but using what we know about Jinchuurikis and genjutsus, my replies hold more probability of being right then yours. Plus Itachi had no knowledge of perfect Jins in part 1 and Kishi had Bee say genjutsus don't work on Perfect Jins in the current story while Tsukuyomi being known by a good amount if people. Cloud ninjas such as Shi shown to know what MS is and Itachi's skills with Amaterasu to compare it to Sasuke's plus Jiraiya knew about Tsukuyomi in part 1 and he spread word about Akatsuki plus they have the bingo book which list known info on criminals which Itachi was in.