My guess would be that his going without food so long has affected his digestive track. Now he has a big meal that his system couldn't handle but it's down too far to regurge it. If you soak him in warm(not hot) water and see if he can move it, that may help, but if his intestine is damaged or twisted or too weak to move the mass on to poo it out, he may not be able to be helped, short of an enema or surgery.
I would advise NOT to take him out to the yard, nor to handle him much, if at all. Let him relax in his cage with plenty of hides and warm humid spots and leave him alone except for treatment. He's not used to being handled, and ball pythons generally don't like bright open space. Roaming around a lawn will stress him because remember, all his tiny snakey brain is telling him is "Any minute a giant bird will swoop down and eat me!".