Any sport these days social media is your friend it takes work and dedication but will likely pay off. You need a good video camera. Video games, edit, make a highlight reel and get it on X and Instagram. Follow every coach, scout, assistant, development guys etc you can find. Email them as well, not you your son. Follow up on the emails, a lot.
Not sure what metrics there are for Hockey but you need to go to a third, unafilliated party and get any and all metrics recorded then put those out there. Here is the hard reality. There are a ton of kids that are good players. There are not a ton of kids that have great metrics. The higher level programs are going after the ones with metrics and good players. They can also do more with kids that have higher metrics, ie a much higher celining.
You should get an independant evaluation. They are available. They will tell you exactly where you son projects. This is likley going to differ from your opinion. If a reputable evaluator tells you that you have an NAIA or Div III prospect don't waste time with Div I or competitive Div II programs. These guys know, they do it for a living.
Weight training and training in general are important. Get videos of training, blast them on social media. Post the strength and conditioning numbers. Coaches want to see this.
Things are changing in all sports due to the transfer portal, NIL, etc. It is getting really hard for anyone other than the most elite prospects to get looked at for any high level programs. The most elite prospects don't fall through the cracks and you don't need to wonder if you are raising one. Target schools/programs that show interest in you. Target places you have a realistic shot at playing contributing. Sitting and watching while putting in the work sucks. With the direction of sports if you deserve a shot at a higher level you will get it. If you tear it up at a lower level the big dogs will come hunting.