Mid January is really pushing it IMO. He should be off throwing for 60 days minimum which puts him at the end of December to begin light throwing. Then trying to get ready for mid January is unrealistic. He is a 2018 for crying out loud - why the rush?
Pitching is not only about arm strength but touch and feel and the whole process of getting ready for a season is about a 60 day process, and this assumes he has a place to throw, In NJ?
I would get him on a weighed ball program first to warm up for the season and then start throwing baseball after about 30 days of developing the arm. I would check out drivelinebaseball or ron worlforth's program. My son's former college program send weighted balls home for the holidays with all of the pitchers to get ready for the season and they were sand so all he had to do is find a wall to throw against.