It's fine if corporations can form syndicates to black list workers, workers can form unions to strike, take over factories, etc. If corporations can then buy its own mercenaries so can workers form their own militias to take on rent a cops. And so on. This stupid fantasy of corporate tyrants free to do as they wish ends the same way all tyrannies do, with a revolution.
Except that many states have now made laws making unionization very difficult. Also, I'm not sure if you intended, but everything you said describes the early 1900s. The Pinkertons were deployed on many occasions to break up unions, and they acted as a mercenary force against the working class. In the end rights were won, and then the 1980s came and Reaganism heralded the destruction of everything that had been fought for under the guise of being 'business friendly'.
I guess so, though there are a lot of examples in history where you ended up with stable feudal-like states. The idea that anarcho-capitalism would produce an optimal equilibrium seems ahistorical to me. I don't think humans have figured out an ideal system of governance, but a strong central government constrained by the rule of law and some democratic checks and balances seems to be the best we've got.
I'm sorry, I didn't meant to say that anarcho capitalism specifically has historically end up in a feudal state. What I meant is that a lot of historical societies, and modern ones for that matter, end up with strongmen oppressing the majority of people so it's something to be very wary about.