I would follow your breeders advice. Some are ok with feeding very soon. I have gotten some that would feed the day after I got them. Also It will not hurt to feed him in his enclosure, there is less stress on them that way. I have over twenty snakes that I feed in there enclosure. I have never had any problems with food aggression. The thing is make sure that you don't make the only time you open the cage is just for feeding. Even so I don't see ball pythons being a problem. Also be sure to use hemostats or some form of long handled feeding device. You don't want to get a feeding bite.