Is there a way to move a verse back to new? I got excited by the possibilities, but so many in "due" is overwhelming.
Move verse back to new?
You can even move them back in bulk 
It is indeed important to keep a good balance of reviewing memorized verses and memorizing new ones. The "due" box is an indicator for this. You do not need to empty it completely every day, but allowing it to get overcrowded is not a good idea either.
See https://www.remem.me/docs/verses/#moving-postponing-or-deleting-verses for instructions