Good god that is a crazy fixated bp. What kind of enclosure do you have him in? Are your husbandry specs within limits? If all that is on I would increase hides and let the guy rest for a week or so to settle in. Changing environments is extremely stressful for snakes. If your gerbil colony is sustainable for the long haul you might not be in such a bad spot.

For shy eaters you can put a blanket or something over the tank while they eat.

Just a thought, but are you sure that your friend was truly only able to feed gerbil pups? Sometimes people get whacky advice and discount other food sources. Ive overheard pet store employees dishing out this nonsense. It might be a good experiment to see if he would take down a young mouse or rat. The change in smell might jump start him.