Empirically, from running a quick script on the data in the article, it seems like you only need to sample 5 numbers to get a distribution that looks uniform using this "sum mod 10" method.
If you're going for empirical, why not ask for between 1 and a very large number? May as well extract as much entropy per person as possible for post-processing.
Mod10, no matter how large the number you’re only keeping the last digit (assuming they choose base 10 numbers), which... is probably no more random than asking them for a single digit in the first place.
A core Libertarian value is individualism. So something like trafficking would be anathema to any Libertarian. Furthermore, I'm sure many would acknowledge that under a certain age it is not credible that any child has the ability to choose prostitution.
I'm not a Libertarian myself, but wanting to reduce the power of the state doesn't mean you believe in slavery.
I don't think you understand what a monopoly entails. Having a large marketshare is simply not the only qualifier. It's also not remotely anti-competitive. That's just not what that word means.