The dogs limited exposure to the world wouldnt bother me too much. Take him out and see how he responds to the world and various stimuli. Test him on surfaces, around noise, people and other dogs.
Shouldnt take you long to figure out what he is at his core.
Test his food drive and object drive after a couple of weeks to determine what motivates him.
Develop a training plan based on these results..shouldnt be an issue y'all are dog trainers.