I recommend that he be sure he understands the placement rates types of jobs and salaries that students are getting in env. Studies Env. Science and env engineering.
In our experience, they are very different opportunity sets. You want them to ideally find the major that puts them in position to get jobs that interest them when they are done.
I wouldn’t recommend the Math2 test in December for a Junior even if he’s mastered the content last year. He’ll be exhausted and there’s no need to rush.
Better schedule both tests in June, when he’ll have a couple weeks to rest, recover from school exhaustion, and prep a little.
I’d keep Vermont on the list for the strength of its Environmental programs and because it seems to mesh with the vibe your son is seeking.
Is he planning to run in college?
Take a close look at Haverford and Bates. Both sound like they would be good fits community-wise and both have top notch running coaches and good/nice teams.
Think about Middlebury - a lot like Bowdoin just mountains instead of ocean and strong in environmental.
Also Williams (if he wants to continue to pursue art in some capacity even if not a major, stellar program).