It’s what he deserves.
No.
MC actually loves the hyung (refer to chapter 2) but decided to push him since the hyungs father discovered their relationship (refer to chapter 16) without telling the hyung the reason. I think the hyung became obsessive because of the MC's action.
That’s not justified his actions tho
I agree that it does not justifies his action in beating the MC and yes the hyung is an asshole by beating the MC but I don't think that he deserves to have his fingers cut off as well. And the MC's trauma doesn't justify the boss actions as well, while the MC is mad and traumatized of the hyung in that moment but I don't think he hate the hyung. They could have figure things out between them if the boss didn't interfere.
Yeah cut off his D too(๑•ㅂ•)و✧