In my experience, P. carteri always lays single eggs. However, since they're capable of laying a single egg every 7-10 days, some egg depositions may be missed by the keeper. This explains why the eggs are laid in different places. In fact, every Pristurus species that I've ever bred (about 6 forms) have all laid single eggs. Careful attention to quality lighting, diet and all husbandry issues is paramount with this species in the long run. They tend to do well at first and then take a quick turn for the worse like a Uroplatus or chameleon.
Jerry, as a suggestion if you're going to use fruitflies for this species I'd suggest doing everything in your power to beef-up the supplements going into your geckos. I'd guess that a large healthy male P. carteri would expend a lot of energy and time trying to fill his gut with such tiny prey - maybe a few hundred fruitflies would be necessary to get an adequate meal.
Good luck!