Okay. Lets answer it one by one..
1) Yes. Pre-cum does contain sperms. But very little, compared to
when you have an orgasm.
2) Whoa. Good question. But yes. I've heard of people who did heavy
petting, and the girl still got pregnant.
3) =_="" If It can't, then how people get pregnant?
4) Sperms generally die a while after exposure to air, if you wiped
it dry, chances are they're already dead.
So meanwhile, if you're really scared... You won't do anything like
that again. Follow-up advice. Get your gf a pregnancy kit, and test
for it a month later.