I think here we diverge of talking only of SG, I 100% agree with you and if we are talking only about a novel there is nothing that I would add, however this is a interative media and while I don't think that authors should limit themselves on the behalf of the player, I also don't think they should be careless with it, you should give as much control over the story and its character as possible. I am fine with chosen the lesser of two evils, with unfair choices and even with choices that we as player don't have enough information to make - you buy the burguer with the sweet or spyce sauce ?- and I am fine with bad outcomes as well, what I don't like is to be stripped down of a choice - here I am not talking about SG- in ordem to have a determined outcome.
About the Nami situation I also agree with you, to clarify my point I feel that if Nami never moves on from the MC even when being "exploit" by him a bad idea not because is in itself a bad narrative, but because in my eyes, given the nature of the story's theme such decisions should be punished, they should lead to a bad outcome to the Mc and have Nami as a spare pussy feels like a reward to a much darker story. In this sense I also agree with Nika growing protective, we have some of that in Vic story already, is a great story and think those choices that diverge from that are the choices that "should" lead to a bad outcome because they go against the story themes. Rewarding a Mc that becomes more selfish don't makes sense in a story that is about open up.
Unfairness is a great narrative tool - I still am not over Bambi's opening or Bridge to Terabithia ending- and in AVNs it can hit more harder because it can be a consequence of your actions that breed a unjust outcome, but still has to have a narrative sense to any unjustness otherwise it is just... I don't know, sadism. For what I can tell we pretty much agree, but we are approaching it from different angles.