Then the problem comes from having to chose between Turd Sandwich and Giant Douche and the solution would be to have someone that knows a little about ruling a country.

voluntarily approached and

So I must have the opportunity to live outside it. How does Ancap theory limit land ownership, and the defence of that land by force? If you don't then nothing about Ancappery is voluntary.

free of violence or harm,

Then there must not be capital accumulation: For resources are power and accumulation of power corrupts even the most virtuous mind.

which is to say that if you do not respect the inalienable rights of the others, you are violating the Contract for being in that society, and you are rightfully gonna be aprehended.

So if you, or ancaps collectively, own all the land which prevents me from exercising my inalienable right to not be part of any of their fiefdoms then they are violating that contract, and will be rightly apprehended by their goons.

I think the social contract thing came into the general anarchist vs. ancap discussion because social contract theory leads to a lot of things Ancaps don't want, such as universal welfare, so people at least on the internet started dismissing it entirely. But it just so happens that you made your own contradiction so I didn't need to recourse to that, you built a contradiction into your description of ancap fundamentals: Congratulations, you back a political suicide cult.