I agree with you. Nameless can see Jihwan is having doubts and is falling to pieces over the whole thing. Everything he says this chapter is very measured and intended to intensify Jihwa's already ever so heavy guilt. He is constantly reminding Jihwan of his involvement and forcing him to face the reality of the situation When he starts describing such brutal, violent acts against Nakyum I suspect he is trying to scare Jihwa off and make him even more uncomfortable.
Exatcly, that's what I think too. I hope we'll get to see more of what kind of person Nameless is.
I kinda thought, that the assassin guy took NK to him to show him that murder might not be the best, easiest and fastes way to solve his problems - because seeing someone suffer and die is different than ordering someone to do it for you, it makes you realize things.
But then I remembered that the assassin killed the servant without hesitation and now I'm not sure anymore ╮(￣▽￣)╭