Wow. Debunking this in whole is a bad use of my time so here's a short take: You seem to think that libertarians do not believe in laws decided by representatives and executed by courts and police. So you don't understand what libertarianism is. Even the school of libertarianism generally accepted to advocate the minimal form of governance, aptly called Minarchism[1] accepts all these things. So your concerns such as:
"Market-based laws will be so ridiculously complicated"
"do you think the law enforcement company will be shut down?"
"what on earth will prevent a crazy misanthrope from lacing popular pain tablets with cyanide, if not the fear of a watchful public police force and centralized justice system?"
apply to market anarchism, not libertarianism. And fwiw, they have answers to these questions, if you bother to look into them. Others of your concerns seem to apply in full force today, despite a massive and powerful government. "Law enforcement agents will take advantage of their authority, abusing innocent people, and victims will face an uphill battle seeking redress."
"Homelessness will exist in every major city, in the very shadows of luxurious highrises and skyscrapers. Poor people will be forced to rely on family and friends for support."
"Institutions of learning will become profitable businesses, with the most popular schools accumulating massive endowments. Universities will solicit contributions from graduates to meet their budgets. Quality will be uneven: the poor will receive below-average education, while families with more means will compete to get their children into the best-rated schools." Many libertarians will argue that these problems are created and/or exacerbated by government, e.g. college is more expensive due to guaranteed student loans reducing student price sensitivity, homelessness is more prevalent due to regulations which make housing more expensive, e.g. most cities require housing to be built with attached parking, which increases the cost of housing significantly. Government policies also encourage debt financing, which add significantly to the actual cost of housing. So, in short, you're arguing against a strawman, and using arguments that apply to the status quo, in whole or in part due to government policies that libertarians would dismantle. Please study up and try again.