Why do you feel the need to "like the protag"? Not every protag is meant to be likeable, relatable, perhaps, but personally, I feel like Eugene is supposed to be an observer and not a partaker, that's exactly why he's doing the things he does in the story. He's not there in the new town to hang out and make friends and do wholesome stuff, he's there because he wants to have fun messing around with people's lives and making them grow.
Believe it or not, I do want to see him succeed in his goals, even if he's a bad person. Because his goals align with what I want to see in the story. And how is any of this story bitter and hollow? It seems to just be a humorous self-serving kind of thing for both Eugene and the reader, which is, you know, the whole point of the novel.
Perhaps that's the whole point of Eugene's character, that he IS a bad person who wants to manipulate people's lives, and one should not automatically expect him to grow and develop into a better person. If he does in a natural way, that's fine, but I'm perfectly okay with a bad person who does bad things for bad reasons, as long as they are entertaining (Like, Jack Horner, for example). I just think that your expectations are a bit out of place.