Should he be sleeping so much? He takes very small tastes of the ND water (which has mash in it) when David puts his little beak into it, but cuddles into David's hand and sleeps most of the time. When he is in the box, he still lays on his back or side, but in the hand, he spreads his little feet out almost properly.
Anything else we can do?
All you can do now is wait and give him some time. as far as sleeping I'd say sleeping is important. mama cuddles hers under her from time to time when they are out and about for warmth and rest. Plus he has been through an ordeal so he needs his rest. so when you put him in his box with his feet down first he immediately goes to his side or back? he won't stand up? He is using David as his mama, he would be cuddling under her to keep warm and feel secure.