Your views seem pretty libertarian. As optimistic as it sounds, empowering individuals with a minimalistic yet resolute government, I don't think our government could ever be libertarian. In a great world and society, where people are informed, intelligent, and internally motivated, libertarianism would be great. However, there are too many people who think the government should do the work for them. There are also too many people who think ignorant people will hurt themselves, such as in your dueling example. Altho there is consent from both parties, can't you see some dumb people using the system? This can be extended to other areas if we took a libertarian stance.Public transportation services wouldn't have that right; nothing that is a public good would, so energy, housing, sanitation, etc.
For the case of child pornography, the people who demand it aren't the same as the people whose rights are abridged/waived, like it is with the demand for smoking establishments, so obviously it's not allowed. Prostitution on the other hand should be legal, with the health caveats I've mentioned.
Duels I don't see why they should be illegal as long as both parties sign contracts absolving the other for whatever happens between them. They also would be restricted such that people who have nothing to do with them are prevented from being harmed, so a 'public place' would be off limits, while a warehouse wouldn't be.
Don't get me wrong. I think that most intelligent people would take a libertarian stance, minimal yet effective government with emphasis on individual choices. However, most people would agree that it's not effective placed over a general population.