Better than 50.5% accuracy actually doesn't sound that implausible, but I will note that if Omega is probabilistic then the way in which it is probabilistic affects the answer. E.g., if Omega works by asking people what they will do and then believing them, this may well get better than chance results with humans, at least some of whom are honest. However, the correct response in this version of the problem is to two-box and lie.
Better than 50.5% accuracy actually doesn't sound that implausible, but I will note that if Omega is probabilistic then the way in which it is probabilistic affects the answer.
Sure, I was reading the 50.05% in terms of probability, not frequency, though I stated it the other way. If you have information about where his predictions are coming from, that will change your probability for his prediction.
EDIT: I see by the karma bombing we can't even ask. Why even call this part of the site "discussion?"
Some of the classic questions about an omnipotent god include