2. And that kind of abuse is not required for non-Force Sensitive slaves because...? I think you're making an artificial division at this point. Especially if cruelties are as you say so expected of a Sith - you'd think any slave would be abused on principle, no?
3a. First, the Dreshdae academy is kinda a compromise on that issue in the interest of cranking out Sith warriors and plundering the Valley of the Dark Lords. Second, about temptation... The thing about Juhani is that despite her anger issues, she's actually a far more stable and centered Jedi than Bastila is, and she doesn't have Bastila's swollen ego. And thinking about it... she doesn't have a big dirty secret weighing on her mind like Bastila does, either. Also, when I brought up fear of temptation as a reason for Bastila not wanting to go, I was meaning to imply that perhaps that was the deeper reason and she pulls the "I'm recognizable" card to cover for it. ...Although, maybe that's giving too much credit for depth.
3b. Ah-ha, but there is a way to know that people are apparently blind to them before trying to infiltrate the academy (which you don't even know you need to do until walking around town and asking questions): The fact that nobody in Dreshdae picks up on the Force-sensitivity of anybody but the PC.
4. Aaaand I think you're getting sidetracked by my use of the "Get away with murder" metaphor (and the wordplay based on it). Your original point was that you weren't going to buy "Sith Arrogance" as an excuse, my counterargument was that K1 Korriban runs on it. Which is why you can get away with all the crap you pull, Light Side (No proof you killed those students) or Dark (you'd think Uthar would be a bit more diligent about his bedroom security, no?). Which is why nobody, not even Uthar, notices if you're a blazing beacon of the Light side and not fallen at all until you tell them.
5. Not necessarily so, especially given that apparently the academy has had people show up in groups before. And Jolee and Juhani aren't famous faces or the targets of Malak's obsession like Bastila is.
For my money... If Calo Nord was that concerned about not being beaten to the punch, he probably wouldn't have given the detailed info about you and the other party members from Taris at all.
Speaking of said info, something that occurred to me after rediscovering that this was a thing: got to love how apparently nobody of note on Korriban has the detailed description of the PC that the random Dark Jedi assassin trios you encounter do.
...maybe, just maybe, there are some loose threads we shouldn't pull too hard on.