Do 5's ever suffer from lovesickness / lovepain?
It can happen.
Are they capable of empathy? Realize when someone is feeling sad or hurt?
Definitely capable, but not as astute as other types. I think that's more of a Enn 4 thing than it is a 5. So, being a 5w4, I have to allow myself to tap into that side of things. And I may not always "realize" when someone is feeling down if I'm in Enn 5 mode. If they show it, then yes. If it's well hidden beneath the surface, it will be hard for me to pick up on. But, once it's shown or brought to my attention, then I actually want to go to that place with them.
Do they ever have a bad conscience when they realized they've insulted or hurt someone they like?
Yes. Very much. I find this to be largely accurate:
http://www.9types.com/descr/5/
One of the bullet points under "What's hard about being a 5" is that we sometimes "feel bad when we act like a know-it-all or when we act defensive". I'd say it's more feeling bad if I've said something out of my rockish nature that really stung the other person. That makes me feel bad almost every time.
What could someone do to really hurt you?
Probably a breach of confidence or a betrayal of trust. I'm big on integrity. Do what's in the best interest of your friends, of those you care about. If you have to sneak around and keep things hidden and engage in all kinds of "behind the scenes activity", why even bother being friends with that person? I'd rather that person cut me loose so we can both get busy being honest and free again. This could be in any different realm: betrayals of trust in the business realm (your handshake didn't mean what you said it did), finances, words spoken to another person, misleading/deceitful actions, etc. Basically, I want trustworthy people around me.
What is the nicest thinig you could say to a 5 to win him over?
I doubt there is one thing that would "win someone over". But, things that have meant a lot to me in the past are things like, "You're a good friend." "I appreciate you for who you are." "I'm glad you're a part of my life." "When I need a solution, I call you." (haha). My ISTJ buddy calls me "The idea guy." I have a family member who knows I don't like talking on the phone a whole lot and so she'll call once a month and say something like, "It's been a while and I needed my monthly INTPness 'fix'. My tank was running low, but now I'm good again. Ahhhh, I feel much better now!" LOL, cracks me up every time. We may not be social butterflies, but we like our time with people to be of high quality. Fun and silly, but also good conversations. Also, my step-dad is ESTJ and we don't see eye-to-eye on most things at all. I probably call him twice a year on special occasions. But, I found out recently through others that he "really, really enjoys my phone calls and our conversations" and that I should call more. That really meant a lot. That's one of those things that gets into the deeper places for me. I know he'd never say it to my face, but just to know that he'd like more than just 2 calls a year - it showed me that we have something more than I thought we did. It gives me something to build on.
What is the worst misconception someone could have about you?
That I don't care. As an example, I have siblings who are sensors and we don't share a lot of of common interests. And because of that, we don't talk as often as we should. But, recently I've made more of an effort and they have all responded in kind. It's been really good to see that "rebuilding" or "re-establishing" of closeness. What I realized is that when I'm distant for months at a time, they think I don't care. Nothing could be further from the truth. I care very deeply. There's just hasn't always been a lot of common ground in the past. But, just a phone call to reach out and say, "Hey, guess what? I care! What's been going on you big lug?" - it goes a long way in showing them that I do care.
If you had a choice between 2 women - one who is emotional, kind, fun to be with and sexy or one who is aloof, intelligent and rational. Which would you choose?
Who would pass up on kind, fun, and sexy? I'd definitely go with the first option. Only exception would possibly be an ENTJ, but they're not really aloof. Intelligent and rational, but not aloof.
But, that's just my personal preference. Even if you're the aloof, rational type (OP), there's someone out there for everyone. There's always someone out there who will appreciate you exactly the way you are.