I like most of your suggestions except one: 9) add a downvote button.
For 2 reasons:
- it foster bad reactions and can be the best tool for trolls
- the best way to show that you don't like something is to simply ignore it. This way, only positive reaction prevails. It is also a way to respect other people opinion.
Imagine you have hundreds minnows upvoting a post to support the point of view of the author. If you have just one whale who don't like the pov expressed there, he can downvote and undermine all the support the post received.