I'm not defining having leverage in a situation as specifically about blackmailing someone into doing something they don't want to do, but rather more of a applying an advantage in a situation sense. It can be done from either a position of strength or weakness.
Jasmine can leverage the MC's cuckold fetish into making him submit to the situation she creates.
But this doesn't make sense, if he enjoys watching, she's not doing anything by "making him submit to the situation", because he already wants to do it anyway. A version of this which WOULD involve leverage would be for Jasmine to be like "now, if you do this favor for me, I'll invite you along on a double date tonight where you can watch the two of them. But if you don't, I'll tell my mom you planned to take me out alone separate from the two of them". <--- but even then that's a gamble for Jasmine, because MC can blow the top off at any point.
She basically is playing her card of "you're a cuck, you wanted this to happen, so be quiet and enjoy the show or else I'll tell all and ruin things for everyone."
Again, I don't understand. How can she ruin anything? The only possible thing she could do is tell their mom, but that would be to Cornell, Julia, and her own detriment as well. When you say it in that way "you're a cuck, you wanted this to happen", there's a tonality like mc is apprehensive, but that doesn't match his dialogue on the max corruption path.
I feel like you and others are trying to write this submissive narrative that simply isn't there in the actual game (or at least not present on the share paths I'm familliar with). I can't speak for the other paths, but consider you're perhaps applying ntr-path logic to a non-ntr path?