Oh dude, it's a fine, fine line, isn't it? :( Think of it this way: If you'd gone through with it, you'd have had to "put up" with being around someone with her looks, which would've just been awkward for the both of you. It's a terrible thing when the nice ones are the less attractive ones. YES looks aren't everything, but there also needs to be a physical/sexual connection, and if you can't establish that, then there's nothing wrong with that, right? I'm sure to another guy somewhere, she's probably attractive (Beauty in the eye of the beholder, ey?), and that physical attraction is something that's a benefit to their potential relationship. Don't feel too bad dude :)
Whether other people want to admit it or not, you can't build a relationship if there isn't at least a little bit of physical attraction. As long as you were polite in your rejection then I see nothing wrong with it... better to let her find someone who is attracted to her than string her along with false interest.
I don't think so. I've rejected people in real life based on just looks. I know that sounds terrible, but you can't force yourself to be attracted to someone. It does make you feel pretty bad though :(
No I don't think so. And think about it, someone you may find hott may find the same girl unattractive. Its all just personal interest. Don't sweat it, your not. Unless the way you turned her down was "nah, I think your ugly" then yes, you are
It depends on how you did it. If you were like "no thanks, fatty", or something like that, then, yeah, that was jerky of you. But, if you were polite about it, it's fine. If you're not going to be interested in her then you shouldn't be leading her on.
You are absolutely not a jerk for doing this. If you are looking for somebody to date the first thing that comes into play is attraction. Without attraction there will never be great sex, and without that you lose one major thing that will keep the relationship together.
Its not like you messaged her back saying she was horrible looking, if you did that then you can feel like a jerk.