I'm not against some online classes. They can certainly meet needs in particular academic subjects and they can be a big help for gifted kids who have need for acceleration. We used them in our homeschool and I've taken them myself as well. Some are of course much better than others, but there are some good options out there. You really need to look carefully that whatever you choose isn't just meeting state standards but is actually provides an appropriate level of challenge.

That said, I'm personally opposed to all online classes for a teenager for a number of reasons. First, I think it is simply not enough time around other people. Even if he's doing one other activity that is still a huge amount of time at home without new people who may encourage him to learn and grow. This becomes more and more important in the teenage years.

With an asynchronous child at home it can be really easy to get into a pattern of taking the easy route of allowing the child to grow in areas of strength but remain in a comfort zone of not stretching himself. The fact that you didn't realize he was such a strong writer before he took the class is a good example of that. Also, the fact that he worked himself up into so much stress over a single homeschool class for me is the best illustration that he must continue to have these opportunities. He stretched himself in ways that he wasn't going to at home and comfortable or not that is something he's going to need to do if he wants to be an independent adult. The next step would be taking a class without mom present. Anything you want him to be able to as an adult you really need to ask yourself right now what are the steps to getting there and bit by bit take those steps.

As he ultimately plans to go to college, I also think it is important for him to get regular practice on classroom skills such as participating in class discussing, handling disagreements, meeting deadlines, taking notes, asking his instructor for help, etc. Also, for him that's going to including handling fatigue and finding ways to adapt and work with his strengths. While some social skills can certainly also be practiced in an activity like theater there are some classroom skills that are specific to the classroom.

With the challenges he has, it is especially important that your son has opportunities to be successful. Clearly his intellect is a strength that he needs to be allowed to develop and doing so will contribute in positive ways to his self esteem. You've mentioned before it is difficult because your area heavily emphasizes stuff like football that doesn't fit with your son's interests and abilities. That's exactly why it is important for him to be in classes or groups where he can shine intellectually. Those may also lead to some other friendships or relationships with teachers/mentors that will be crucial to helping him avoid loneliness/depression in the teenage years.