I know this is Kruw's AMA but as a 15-year AnCap heavily into seasteading, I'd like to take a swing at this answer.

Governments own and are sovereign over every square inch of land on this planet. They have been since long before we were born, and that makes it very, very hard for anyone alive now to understand what it's like to live outside of government control.

Most people, when hearing answers that libertarians give them, will automatically imagine those answers being deployed in the world they already know; which is nothing like a world outside of govt control. They won't solve problems here in this world.

Even if you want to homestead out in the woods on land you rent from govt, then the problems you come across will still exist, and be unique to your location and distance from resources.

Questions about who puts out the fire and how to deal with public domain issues of any kind isn't hard for libertarians to answer, but it is very specific to the place they hope or plan to attempt such a free society. Their "platform" will dictate the ultimate answer. Even two different seasteads could be designed very differently and therefore call for different answers to public domain questions.

You can probably imagine that living on a fully self-sovereign seastead that has its' own courts and law would be very different from living on a seastead that is flying the flag of another country. The latter has to abide by the laws of some pedophiles thousands of miles away. Those countries have existing regulations that seastead B would have to follow, even when they don't make any sense for the locals.

As for the economic question you posed at the end, different societal systems will have different economic challenges too. What causes poverty there isn't what causes poverty on land. For a fully self-sovereign seastead with no government of any kind, I imagine something like Assurance agencies would be a very basic service that everyone will consider as important as food. Without an assurance agent to have your back you wouldn't enjoy the protections that police & lawyers offer you today.

I don't claim that this system is better in every way to what we've got, but It does allow for civilized society & public domain in a decentralized way, all without being ruled over by pedophiles & warmongers.

Why I promote seasteading: Govts aren't going to sell land to us with any sovereignty intact. That's just not something they do. We have to either build our own land, or race to some new land out in space first before we'll ever have the chance to be free.

Living off-grid isn't appealing to me at all (neither as a lifestyle or a political strategy), it's practically synonymous with poverty. As we saw with Ruby Ridge, isolation doesn't stop the government from marching their army to your doorstep in order to enforce their petty regulations.

Anarchocapitalists embrace markets and reject governments. The solution to all of the problems you listed is "money". Specializing in your own career and simply hiring a plumber, doctor, butcher, & firefighter is way more efficient than becoming a "jack of all trades".

Who's got their back when someone comes to take their shit?

The market for violence is a tricky one. Arguably, governments are competing against their citizens and competing against each other in the market for violence.

Emerging technology can shift the balance between attacker/defender advantage. Finally, after thousands of years of tyrants stealing livestock, crops, and gold, Bitcoin has arrived to liberate us.

what about the ones who can't afford it?

Poverty is the default state of man: He is born naked, hungry, and unsheltered. Anyone who wants to avoid these conditions must work to provide for themselves, or work to provide for others and trade with them.