So far, with the blackmail, Dylan has achieved nothing for himself. I can't find a benefit for Dylan with the blackmail. I would say that only Sophia's students benefited, no one else. And a little bit, Alyssa, knowing that Sophia goes to class without a bra, maybe, has given her courage to go further.
Dylan has achieved everything without the help of blackmail, as if blackmail did not exist. Besides, seeing her in a short skirt is much less than Dylan has seen so far. It is true that after bikini-show or showing Dylan her tits, things did not progress much.
What I mean is, now that Sophia has shown off in class and in order for Dylan to gain something from his plan, Sophia has to go around the house less dressed. That's what Dylan expected, right? Because, so far, only Zac and his colleagues enjoy it.
What's in it for Dylan?