The problem is that the "Next" link is easily overlooked, and the users want to press the "Submit all and finish" button because it's more visible to the eye.
I've already modified the code per another poster's suggestion such that the user can't backtrack and don't see the numbered links to subsequent/previous questions.
As far as Navigation, there's the "Next" link, and buttons for "Start Over," "Save without submitting," and "Submit all and finish."
Again I'm looking to turn the "Next" link into a button instead.
Screenshot attached.
