I'm asexual, so I can't help with most of your dilemma but as for your last section... I would say the difference between a friendship and a conventional relationship is the emotional connection, not the behaviours that you perform with that person. It's up to the two people involved and how they see each other and their bond. After all, two friends can have sex together, but that doesn't make it a relationship. Two asexuals can be in a relationship but not have sex. It's just that people nowadays see sex as a really big thing and there are really other things that make a relationship.

I would say in order to be bisexual, you would need to experience sexual attraction towards men and women (not necessarily "like having sex", because not everyone enjoys the full acts even though they may be sexually attracted to a person, for various reasons, and some people who are not sexually attracted to people can still enjoy some sexual acts- such as kissing, in your friends' case). I do also wish to add though that not all bisexual people are also biromantic (wanting relationships with both men and women). My brother is a heteroromantic bisexual, meaning he's sexually attracted to both, but he only experiences a romantic desire towards women. People of other orientations can also be biromantic (so asexuals, heterosexuals, homosexuals etc).

I don't know about how many straight people kiss each other, but considering I've heard of straight people experimenting or enjoying more than that, it wouldn't surprise me. I'd certainly say I'd expect more women to be publicly kissing than men though!