Thanks for the props on my running. I have also been blessed to have worked with a 1:49 and a 1:50 800 runner so that helped me extend what I knew from my own racing.
The # of races scheme is derived from research and from experience. I would say that it depends on the level of competition in the races. In hs, you could probably get away with running more races because the early season races tend to be not as fast (usually due to the weather in the northen US). I feel like the issue of mental freshness (which you correctly associate with the art of the sport) is important. I feel as though you can create bad habits by racing your prime distance before you are into specific prep.
Having said that, I can suggest time trials at sub distances to alleviate the desire to race too much. The lower the distance, the more you can get away with racing often. In the collegiate system, you can get around this by having the athlete run on relays. I like having an 800 runner run a 1200 on the DMR as well as a leg on the 4 x400. I would do what you could to encourage your athlete to run a distance higher and a distance lower as often as you can-I would run higher early in the season and lower all throughout. That will force him to learn how to run faster more efficiently.
I not saying your race scheme won't work, it surely could but the more you can get in these other items the better. Good luck to you both, let me know how it shakes out.