I think my hesitation in believing Willie to be a real danger in a fight is because, so far, there's been nothing to back it up. We've seen him leering and mashing on a couple of women and threaten/challenge a couple of men to a fight, with fisticuffs always being avoided due to Jason (because it serves his own interests, granted). Perhaps the writers opted for a more subtle approach, but I still see it as bravado. I would have liked to have seen something. We know Willie is volatile; trying to win some money in an impromptu poker or craps game on the docks and busting up a guy when he believed he'd been cheated or something like that. Even if Jason and Willie just talked about the incident. That being said, there's definitely a creepy, predatory rapist vibe in Hall's Willie. There's no doubt in my mind that, given his temper, Willie would abuse a woman. I get disturbing images of him beating a prostitute in a dingy motel room because of a quibble over payment.
But I'm not sure Jason has Willie under control. He could do nothing to prevent Willie from joining him at Collinwood. Willie had the upper hand there.
Perhaps I didn't think through or express the thought well enough. Willie's a brawler and Jason's denied him the opportunity to do what he likes and does best, fight, by metaphorically neutering him and that may be why I see Willie as posturing as a tough guy. And maybe Willie is starting to think that's how people perceive him and he resents it. Jason, by preventing his friend from fighting and withholding info about the 'big job' has, in a couple of ways, emasculated Willie. Not being fully aware of the plan, what's going on at Collinwood and stuck in a lousy rooming house, Willie had to adopt another tack, taking a page from Jason's playbook and using it against him. Willie's turned the tables and gotten the upper hand by using his brain, something Jason hadn't bargained on. He underestimated him, probably believing he always had control over Willie, until this critical mistake.
I'm starting to wonder if any of that made sense.