"How much is he taking in the overnight feeds? If he's bottle fed you could try offering water instead or if BF then a paci/dummy (although if you go down that route you have to think about paci weaning too)."
In the first book Tracy mentions the paci thing. (page 186) The first night give the paci instead, kid will suck whole 20 minutes before falling back to sleep, next night it may cut back to 10 min, the 3rd night he might fidget in his sleep, if he wakes give him the paci. substitute oral stimulation of paci for the bottle or breast adn eventually he won't wake up for it.
good luck.