And I guess that the box at the bottom of all of the posts labeled vote! is for awarding a point to the discussion as a whole if it seems meritorious.

The "vote!" button is for submitting all the votes you have allocated with the radio buttons previously. Just selecting the radio buttons without subsequently pressing "vote!" does nothing at all.

In all other aspects you are correct. See the section entitled "How do I vote?" in Voting/Experience System for more info.