First advice I could give is don't repeat unless he needs it academically. Repeating for hockey will help in 9th/10th and then hurt in 11th/12th. Better off staying in grade, graduating and then if needed, go play juniors for a year. Playing against kids so much younger and then hoping to jump righ to college is a mistake.
Depends on the kid - some kids need to repeat because they are physically not ready to play prep hockey until they are a repeat Jr.
At 13 he's still young enough to take-up lacrosse. If he's not athletic he can go D-3, if he can run and has some stick skills go D-1 and no Juniors or repeat years . . college at 18 graduates a D-1 athlete at 22. Hockey is a foolish path.
You clearly have no knowledge of D1 lacrosse.
Not really true, especially for defensemen. More late bloomers make it at defense than kids considered top players at Freshmen and Sophomores in high school. Part of it is a size issue but usually it's the kids who keep working at their game and don't get showered with 'can't miss' accolades.
Says the dad of a kid who never saw D-I varsity ice until his senior season and then 10 months later made a top USHL team while all the heavily touted kids in the region went on to play Club hockey.
Check your notes, a 'stud' 14 year old defensemen rarely makes it.