Hermes, you cover a lot of ground. A few comments:

These philosophers do not assume a simplistic dichotomy between pain and pleasure. Both Epicureans and Utilitarians are explicitly aware that sometimes a long-term or higher pleasure requires short term pain. That’s why they invoke what they call the hedonic calculus.

When you say that in sports the challenge of improving oneself erases the distinction between pleasure and virtue, I’m not sure why you bring up virtue. There is no virtue in sports, it’s just something we do for pleasure or competitively. It has nothing to do with virtue in the sense being discussed here.

When you say that my analysis does not fully account for the richness of human experience, you may be right, but it feels like you’re raising the bar a bit too high for a 2k word essay. Let’s discuss what I actually wrote, not what you would have liked me to write.

There is no such thing as the naturalistic fallacy. Values are connected with facts, according not just to the Stoics and Epicureans, but also to modern primatologists (de Waal) and some moral philosophers (Foot).

I agree that social cooperation is not an ultimate good, it — together with reason — is what guarantees eudaimonia. When you bring in xenophobia you are missing the point, that’s not social cooperation in the sense intended by the Stoics, which is explicitly cosmopolitan.

Similarly, when you say that the value of reason depends on the circumstances you are not using the Stoic concept of reason. They talk of “right” reason, meaning of prosocial, cosmopolitan-oriented reason. In these discussions one really needs to pay attention to how words are used, otherwise we risk talking past each other.

And I don’t use the word happiness because even modern positive psychologists largely stay away from it. It’s too flexible and mushy a concept to be useful.