Re: correct/total vs. incorrect/total... I'm going to stick with correct/total - I believe this is probably the more common approach that people are used to.
Perhaps down the line I'll add an option to show incorrect/total instead, we'll see. It would be an easy thing to do, I'm just not sure how much I want to clutter up the quiz options with little bitty features. Starting out I aimed for a very simple quiz with simple options that the majority of people would want. I've looked at some of the other, more complex quiz plugins out there - and there is just SO much going on with them, it's hard to keep all those little things organized and intuitive. But I certainly am not ruling out the options - there are of course more features that I'd like to see and that have been requested.
As for the messaging - yes, you're doing exactly what I anticipated. When building this, I figured that not everyone would want to display the words "Correct", "Incorrect", "Right", "Wrong", etc. so it's pretty much my intent for the manager of the quiz to input the messaging they want to use. It leaves a lot more room for creativity and even formatting / styling. For example, you could set up a response like:
"correct": "<h3>You got it!</h3><p>That's exactly right.</p>"
Which would give you a more interesting and eyecatching response (since it has header text) that might look somthing like:
You got it!
That's exactly right.