As a 5, I feel emotions quite strongly in my solitude. It's when I'm around others that those feelings are suppressed out of fear of getting too involved and becoming vulnerable to other people, it's only when familiar with people that I open up more and become lively. I know some 5s that seem completely robotic, their voice is monotonous, their speech so formal and to the point as to hide themselves. Other fives hide behind passivity, they might smile slightly, try to be nice and polite until they feel safe enough to let other people into their lives.
From the looks of it, the other half of yourself that you describe is your behavior in a safe environment, with a select few friends or family that you feel comfortable to be with you can be more like an 8, showing more aggression and being more confident.
The rarity of type 5 women and type 2 men could be due to mistypes, but I have no idea how they gathered those statistics.
Such a 5 question, exploring the systems limits are we?And another question: Is it possible for somebody to be permanently in the middle of a line instead of being in one point? Or the person only moves along a line in certain situations, when stressed or secure?
Everyone has a little bit of each type within themselves. All of the 'types' are all just habits, patterns that we follow, something that drives us to behave in certain ways. There is generally one habit that we are fixated on that hinders us the most. In this way the types are fixed into place as points on the Enneagram. For five, they have a habit of sitting back and observing to defend themselves, but it's not only 5s that will do this, a person of any type can sit back and observe, the difference is that type 5 is more fixated on it, it's their default mode of behavior.
Within each type there are psychological levels of health that manifest in different ways often resembling other types on the Enneagram. Your level of psychological health is dynamic, so like you said, it will change when stressed or secure.
I think this details it perfectly: