Starting for the new season

Okay.My son is 13 and is starting getting his pitching arm back in shape for the new year.I’m gonna admit that over the last 2 years between catching and pitching during to many games and the workouts between games he over did it.The last 3 tournaments he could only go about four innings before his elbow hurt.So he sat out fall ball and played basketball.How many times a week should he throw?how many pitches?this is all for practice.Then when the games start and he pitches one game a week then how should he practice? THanks