In the real world, open markets and free trade don't exists. So considering most of your views can only take place within a managed market with managed competition - ah fukk it....
You have to go above and beyond to explain how libertarians are "nothing" like conservatives, because you're not liberals.
Except in the real world open markets and free trade does exist, mainly on the local level.
We also know that when evaluated freer managed markets are better in producing for a society than unfreer markets, and can conclude as has been done since the 1800s that free trade would provide internationally, better service for the world than managed markets.
So we can disregard your claim of free trade not being feasible off the bat because your initial contention is clearly wrong in its face, of there being no practice of open markets and free trade in the world, garage sales, barter, all being examples of free trade in the real world. We can also disregard your critique as falling into the fallacious argument category close to appeal to tradition, of since its not what is used and always used it must fail.
As for libertarians not being conservatives, its easy, ideologically libertarians aren't conservatives, beliefs in government, interventionism, and economics are opposed to traditional conservative beliefs, same with neo-liberals/progressives. So libertarianism is a defined body of political belief that stands on its own, if you expect to be able to actually have an intelligent discussion on points with libertarians, it would be beneficial for you to take the time and actually ask or research what we believe.
Now if you want to learn more and ask questions or be directed to some sites that explain our ideology, let me know and I'll kindly answer questions or send links your way.