I'm going to discount the more facetious parts of your post and try to give you some straight up advice on the assumption that at least some of it is serious.
He can play HS hockey. Not saying he will be a stud, but he can do it.
He can't make himself taller, but he can make himself leaner. Chances are, you will need to change his diet. When you lose weight, you don't lose fat cells, you shrink them. His DNA dictates the number of fat cells. His diet and metabolism dictate how large those cells are.
The weight loss will make him faster (Zolak talks about how the 40# he lost is the equivalent of walking around carrying a full propane tank), but that will take time. While that is happening, he can build faster feet and explosive speed. That means hitting Mike Boyle on the North Shore or Dan Boothby South of the city and asking for an individualized program to do both. He will know how.
Good luck to you. I will say, even if he doesn't eventually make his team, he'll still develop better life habits and feel better abut himself.
Back in the old days you just throw the fat kid in the net.... some still do that and it will likely get you into peewees and then the slide down the latter comes as he will be unable to move side to side etc and he will slowly go from color to color finding his way to the bottom ranks... that said if he is having fun and meeting nice kids enjoy the ride.