"Indisputable"
I do not think that means what you think it means...
I'm gonna come out and say it.
Everything you've been saying in your current train of thought is completely bullshit.
ß
ßß is the Tri-Beta fraternity symbol. "scientia potentia est" is their motto, 'cause you know, learning (what the TriB's are all about) leads to knowledge.
"Have you done your homework?" is just further emphasis on their expectation that all members excel in their studies. It's not DPC asking you, it's Magnar reminding his cohort.
Everything you've discussed is not an "indisputable" clue at all. What it is, is a stretch of the imagination, and an extreme one at that.
Just for the record, to my knowledge, none of your extreme theories have ever panned out, like ever.
β = beta
ß = sharp S
It's clear that all those posters contain the beta symbol, and not the sharp S (clue: look at the tail dropping on the left).
I've booked him in for Friday, make sure you're home.