On second thoughts, I see what you mean by “Epicurus was a philosopher first” in this context: Something like prolepsis is an important concept within the overarching philosophy even if it doesn’t directly relate to happiness or maximising pleasure. I agree with you on this, and my example of “I know that I want to feel good” was just an example of how I don’t need to know about something fully in order to enquire about it - it was not me saying that Epicurus’ philosophy is only about “the means of happiness”!
The rest, however, I am still unsure about.