Capitalists can't exploit anyone, as their success is based on demand. If individuals are demanding something and a Capitalist provides the supply, it's not exploitation. Your statement is based on confusing profit and exploitation.
Other companies copying a product would lead to more competition, which is better for all buyers. After that, it comes down to improving that product and selling it for a better price, as simply having a similar or same product is not the end goal, it's having a better product for a better price. Even then, it also depends on the individual, as some would prefer a cheaper and lower quality product, so that they may live within their means. Your oversimplification does, however, suit your understanding, that being minimal.
Their roads and bridges would have to be safe and efficient, otherwise nobody would want to travel to that location.
Businesses would simply incorporate the cost of private security into the cost of their items, or use their surplus to pay for it. Since it isn't police, they'd be half the cost, and more efficient. Not only this, but they would have to compete with the other private security businesses offering their services as well. Furthermore, private courts would be more efficient than state courts, they wouldn't submit to the will of lobbyists, otherwise their reputation would be ruined and they would receive no more customers.
Capitalists aren't predatory, they seek to maximize profit and minimize cost. This results in needing to meet the demands of their customers to the best of their ability. Furthermore, simply jacking prices up after competition is gone would result in more competitors rising up and meeting customer demands better. Not only this, but operating at a loss wouldn't eliminate competition, it would take a very long time and cost a fortune, and can't be permanent, as in order to create a permanent monopoly, they would need government help, OR permanent control of ALL resources used to build the product, AND would need to ensure that no OTHER resources can be used to build SIMILAR products.