It sounds like he has a good fit, academically and emotionally. The grass is not always greener. As others suggested I would see of he could get put in a high level Summer team. And the summer season is usually longer of the 2.
My son played at a D3 and played in the Great Lakes and Valley league. He competed very well. I know D3 players used to be able to self release. not sure it is true anymore. And if he self releases his current coach will know very quickly.