my data on kitten intro timelines

I am posting my current data set for a new kitten introduction. I have a 6-year-old tortoiseshell, Willow, who has allergies, and a 2-year-old domestic shorthair, Rio, who currently has fleas. I completed a 7-day scent swapping protocol. I am now looking for the optimal number of days to wait before initiating visual introduction through a barrier. I want to minimize stress variables. I have seen conflicting advice on forums. Does anyone have a concrete timeline for this specific scenario?

I just adopted Koda, a 1-year-old mixed breed. He is going home with Kiki, a 5-year-old Siamese who is very anxious. I am terrified of doing this wrong. I read a thread about stopping scent swapping but it didn't give me a number. How many days did you all wait? I feel like I am overthinking the logistics. Is 7 days enough? Or should I wait longer because Kiki is sensitive?

I have Pepper, a 1-year-old calico. She is scared of the vacuum, which is a problem because I need to clean up after the new cat. See Pepper and the vacuum for my struggles. I think the main issue is not the days, but the environment. If the room is chaotic, more days are needed. But I don't know how to measure chaos. Is there a metric?

I have Leo, a 1-year-old tabby kitten, and Bella, a 3-year-old rescue. I think age matters. I found a thread on kitten vs adult timelines that suggested shorter periods for kittens, but I am not sure if that applies to adult cats with health issues. Rio has fleas, right? Does that change the math? I am worried about Bella catching something. I am just a marketing associate, not a vet, so I rely on you guys. What is the safe minimum?

I am a nurse, so I understand protocols, but cats are not sterile operating rooms. I have Loki, a 1-year-old Bengal, and Freya, a 1-year-old Ragdoll. They are very different. Loki is high energy. I think the "days" metric is flawed because it ignores individual temperament. However, I see what wrivera is looking for. I read flea treatment before introducing new cat and it says to wait until the fleas are gone. If Rio has active fleas, I would not introduce him to Willow yet. That is my clinical instinct. But is that the same as the "waiting period" for scent? I am confused. I need to know if I should pause the scent swapping or continue it while treating the fleas. I am overthinking this to the point of insomnia. Please tell me I am doing this right.