We don't really know as far as I understand. There's been lots of theories about it obviously, suggesting that Quinn, Burke or Vinny were involved in that. But nothing concrete at all.
Melanie might be Troy's sister, it's a theory that's been around for a long time now. I'm not sure that there actually were any demands because if you think about it, Chad thought that the MC was the one blackmailing him and if you paid attention to the dialogue after their fight, Chad literally asks the MC "What do you want from me?!" as he's crying. But yes, probably someone who wanted him and Sage to break up for whatever reason.
Dawe. In the scene at the gym when Troy walks right by the alphas, Dawe starts trash talking to him by telling him to keep on walking and when Chad tells the alphas to ignore Troy, Dawe starts provoking him by implying that Chad's "going soft" for Troy as he says. After that, Dawe says something about Troy apparently having broken his jaw and that it took him weeks to chew properly after whatever scuffle they had. So, Dawe was probably talking about that time when he stormed in Troy's (and the MC's) dorm with whoever else since I don't think they'd be fighting each other back when Troy was part of the alphas either.