Yes, I am willing to reset the theme. Unfortunately I don't know how to do that though. Okay, got it no deleting embedded objects.
No we do not allow users to skip questions.
In that case you need the Clear button, to be able to drag the Next button under that clear button. That way, the user cannot click the Next button during the quiz, because it is covered. During Review, the Clear button disappears automatically and the Next button will appear.
More ideas like this in:
Question Question Slides in Captivate - Captivate blog
Apparently the White theme has been messed up, since that button is gone. The themes you are working with are in a copied folder in the Public documents\Adobe\eLearning assets\Layouts. You'll probably see the date on the White.cptm has been changed. You can put back the original theme from the original Layouts folder, which you find in the installation folder of Captivate under the Gallery. More about themes (which you seem not very well familiar with):
What's in a Theme - a Template? - Captivate blog