I understand all that, I just don't agree; I think this is a stupid idea (not that you are stupid, obviously).
The MC isnt locked into a role; if he was, he'd have acne (like I did, wtf), and he'd be overweight. If there was an overpowering need for him to be the villain, he'd be one.
He isn't.
So he shouldn't be.
It's that simple, both in life and fantasy.
(Also, you kinda added that bit about being killed by his dad, didn't you? Not to be rude, but dont you think you adding reasons for the character to think stuff isn't entirely intellectually honest? I know he should be worried about his family doing stuff, but that's not a thing he has said; just that his father/family would cut him loose to die or fail if he became a burden... which is a great reason to simply cut those ties and become the good guy he plainly wants to be!)
(...unless I missed it)
Have you not been reading this manga??
From chapter 5 (you know, the one prior to the current chapter that you might have forgotten since it was released a while ago), he discovered that he was being poisoned all along under his dad's orders. He says "there's a good chance Luke will be killed at the academy" referencing all the routes Luke will die, and follows up with saying 'however as long as my house is not save i have no choice to move', referencing how his own dad is plotting against him.
Then he follows that up with (and you must have missed this) "I will help the protagonists from the shadows, set the table for the conflict between the royals and nobles, and just like the game, crush duke Deskutos (his dad), the leader of the nobels. This shuold be the easiest path with the highest survival rate, but the fact that this is the world of a game I love hasn't changed. I'm realizing again what a difficult character I've been reincarnated as. I'll be playing the role of Luke for all it's worth. I'm not about to sit back and let myself be killed."
ALL this in chapter 5 which explains everything, his motivations, and knowledge of the game, and how he knows his dad, who has been poisoning him, is the most dangerous foe.
So let's go to the one line that set you off on your tirade. "I will support the protag using knowledge from my previous life while playing the role of Luke, the
villain that's always nearby. I need to avoid the normal routes where Luke dies. Although it may already be set to develop very differently to the game, since I'm no longer the fat, ugly toad, I need to surive for their sake."
You are mad because he accepts the role where he plays villain because of his family, without at all understanding that he has knowledge of all the different ways Luke dies in the game. That he understands Luke dies in every route and thus has to be careful about carving out a path for survival. He clearly states that the plot will be different from the game but he still needs to be careful.
Now, about his dad, intellecutally dishonesty is when you just ignore plot points of the manga from the previous chapter and only focus on one sentence. Did you miss that his dad was poisoning him, and then you fail to make the connection that hey the dad probably will kill me if I go too far out of line? I certainly wasn't making that up you just missed it. Also I didn't want to have to say this but I guess it's not fair for you otherwise, but this is an adaptation of a novel that already has nearly 400 chapters so I mean...
Also his underlying personality is a) kind of lazy and just wants to enjoy life of leisure (this is stated like in every chapter) and b) really likes this game universe and the characters (this is established in multiple chapters too). I really wonder what you think his reaction should be? "I will be a naive protag-wannabe, and do good everywhere!" He's already clearly a decent person, he doesn't do anything villainous, so you really don't have a reason to hate on him. As his family is the final boss of this game, he will be associated with the villains, but within that he will work to ensure the game goes to a good ending. What else could you ask for? It makes no sense why you think his mentality is bad. And finally, that he is lazy is part of the novel/manga title itself and his number one priority has always been to live a fun slothful life and survive so he can have fun with his family and friends. If you don't like these types of characters then this is probably not the manga for you.