OMG. Sorry for spamming in the comments, but I have another theory now.
In the end if ending 3 we can see broken bottle of wine and two glasses. Well, I guess Vincent wanted to eat with Rody that Dead plate and see if Rody will get a taste or not. After that he could kill Rody and eat him as well.
Why so?
Vincent already told us that it doesn't matter if it's a human body or not - he's not a cannibal, he just wants to feel taste again. But that feeling is connected with another theory of Vince's life - love. He was told a lot of times that he cooks without love, but "he's not a parent that makes a meal for their kid". Yes, he is not. He is far more than that - he is a professional chief. That is why... he must cook something his client loves.
Literally.
He prepared a dish with the love of Rody's life, Mannon. He wanted to know if this works out, and if so - he can try to eat Rody. I want to believe that he wasn't going to kill Rody instantly, but Vincent is a hot-tempered guy, which is why, well... he could plan something like that, even if trying to eat only a part of him (his blood or his ear) would be more convenient.
And I noticed something else. We know that Vincent doesn't feel any taste at all, no matter what he eats.
But after biting off Rody's ear he said: "Don't flatter yourself. It would have been better cooked."
HOW THE HELL DID HE KNOW IT?
He doesn't feel taste anyway, why was he so sure that it would taste different? Maybe because he actually felt something, huh? That is why he was so desperately approaching Rody during the last minutes of the game?
Vincent knew that he felt different after all and he wanted to taste more of Rody's body. Maybe he wouldn't kill him, but immobilize him by making severe injuries or tying him up again and getting to his place. Whatever.
Now I feel like I know why he was doing all of this... I hope that I'm close to the truth at least.
But I still don't get who the hell was that shadow-dude in the window of Vincent's bedroom and why he ended up the party so suddenly.