Norcal, Sincerely wish you and your son the best moving forward whatever you choose to do.
For me, this is a no brainer.
#1: Scrap the HS season. You are just throwing gas on the fire & he is admittedly not going to really be a factor at the Varsity level given current status.
#2: 6'2" 140. Forget throwing & get in the gym 4-5 days a week & get on a proper diet to add good, quality strength & mass.
#3: Have him take the weighted baseball, turn towards a wooded area & throw it as far in the woods with his non throwing arm as possible & leave it there, forever.