Re Shiva/ Disu: if we compare the first kiss scene and the last few episodes, there's actually a few things that have become quite clearer re Shiva's pov. Not meant as justification, but just trying to understand the track here.
1. Shiva has NO interest in Disu.
Neither does he want any rishta nor does he want to spend any time with her. However twisted his words, first walk mein hi, he told her that yeh Maa ki vajah se hai.... after the competition, he said that Raavi and him still have something and Disu shouldn't interfere....aaj ke random out of the blue vale smile compliment ke baad he told her stay away.
In his head, he's clear that he's said no already. Ideally, things should have ended there. But we are seeing how persistent Dayan is and how her behaviour is escalating 🤔 Though he tries his best to get away from her, when he sees Raavi getting jealous, he's more curious to know the reason for that than to bother with Dayan. At that moment, only Raavi ke reactions matter. He has no attention to spare to anyone else. Dayan can be as nice to him, nothing registers. This brings me to my next point.
2. He DOESN'T like Dayan's filmy baatein.
He's been subtly trolling her since the first baatein achi kar leti hi dialogue. Imo, it was his polite, don't know what else to say response to her dialogues that had instead gone over his head 
Even competition ke baad, he again gave an indirect to her jalebi baatein 
Finally, aaj he said ki uske filmy dialogues ne life barbaad kar degi 
Even for her smile vala compliment today, he had mocking smile ke really??? Contrast that with his reaction to Raavi complimenting him during that Haveli sequence, he was so flustered. Its only Raavi whose taunts and compliments affect him and get an honest reaction. Again, Disu doesn't matter.
All in all, he's playing a waiting game with Raavi. If Disu happens to be the reason jiski vajah se Raavi is reacting, he's taking that as opportunity. Nahi toh 2 minute ka bhaav na de 🤪