Please stay away from Babywise! THe author has *zero* medical training!! She needs to follow baby's lead for feeding and sleep. Not baby following her lead.
Yes, it's hard but all babies are different and not all babies are angel babies. Some are high needs. Like your grandson. Buy her a mayawrap and tell her to wear him as much as he needs. That is comforting and soothing. My mayawrap was a life-saver with my high needs preemie.
Dr. Sears also has good information on parenting a high needs baby.
Google 4th trimester. That is where he still is. He still wants/needs/craves the comforts of the womb.
Is she nursing? She may look at doing an elimination diet to see if that helps. It can take a few weeks for things like dairy and wheat to clear her system so it doesn't work over night.