The assumption in benchmarks is of course that the results carry over to other use cases. Here, what is being tested is the overhead in recursion, nothing else. The fact that it happens to be Fibonacci-numbers that is being computed is irrelevant.
That shouldn't be possible. If you have a code example, I (and probably other people as well) will be happy to look at it.
Julia has a lot more potential for optimizations than python, but what python has going for it is the larger ecosystem. So if you want to write a one-off experiment that's similar to stuff that already exists in C bindings to python you should use that. If you plan to write a large application that you still want to optimize for current processors in 10 years then I'm not sure if python is a good choice.