Thanks @CT1417. Yes, he’s specifically interested in majoring in physics with CS as a possible minor/double major, so we think the Physics and Math II tests should be fine. The websites of a few for-pay college consultants say that more is better for subject tests. I’ve not become convinced of that except in the special case of homeschoolers, which is not us.
For the OP’s mathy 9th grader, I wanted to agree with the other posters who strongly suggested finding a way for him to take math (not just AP stats) somehow from 10th-12th. Stepping away from math would not be good for a STEM kid, and I wouldn’t suppose the a kid like that would like not learning math, whether it is transferable or not. My son took Calc BC in 10th, so we only have 2 years to cover, not three. We are figuring things out semester by semester based on community college schedules. Currently, he’s taking Discrete Math, which is a math course commonly offered in CS departments.
I know you said your son had a negative experience with an online class. My son also prefers in-person classes to online classes, because he knows he had trouble committing the time if the schedule is too flexible. He did do 3 programming classes though AoPS, and kept up with those. But, he ended up deciding he preferred their Precalc book to the class (partly because he had schedule conflicts that wouldn’t let him be in the class real-time). Anyway, there are a lot of different delivery models for online classes, and one might work better that the other. My son may have to take online classes if the community college doesn’t go back to offering late-afternoon or evening post-calculus classes.