It already shows your current rep in the postbit, 1.6 has the ability to give rep to a user for a specific post.
Not entirely sure what you're getting at but we're not going to make big changes to how it works near the end of the beta. You can give reputation to a user for a post, or just a general reputation, and it all counts to the overall rep.
There is only one reputation, not one for posts and one for overall.
Yes, the reputation, though you can repute a person or their post, all adds to the same reputation. If you want them split that would have to be your own hacking to do it. I don't know how many people would want multiple reputation systems like that. Perhaps one for people and one for a sellers reputation if you sell things on a forum, which is already a plugin. :p