Julia I agree with the thrust of most of your post but as to this I am not completely clear on what you are saying:
In my opinion, getting fancy with "desire"/"desirable" and "pleasure"/"pleasurable" would be like getting fancy with emotion-words, like "happiness", or, more precisely, with experience-words, like "joy". When first grasping the word, it matters to be precise about the inner experience it refers to (eg something fun-but-forbidden may cause joy and guilt, pleasure and pain; it matters to delineate that honestly, precisely, without getting hung up on morals).
At the very least, as to pleasure, it seemed absolutely clear to Cicero, and I would say to Norman DeWitt and now to me also as the only logical way to read the texts, that Epicurus was in fact taking a very non-standard and radically different stance. He was redefining "pleasure" to include not only sensory stimulation but also all other experiences which are not painful, even if not normally considered by the majority of people to be included in pleasure. I see no other persuasive way to explain numerous statements by Torquatus, including his response to Chrysippus' "hand" argument.
I don't see you referring to that his expansion of the definition of pleasure in your comments so far. I think it's important to take a position on how Epicurus was using the word pleasure in a non-standard way to make any sense of many highly reliable texts, including but not limited to the Principle Doctrines and the letter to Menoeceus themselves.
The line from DeWitt that's right on point is from page 240 of his book:
Quote“The extension of the name of pleasure to this normal state of being was the major innovation of the new hedonism. It was in the negative form, freedom from pain of body and distress of mind, that it drew the most persistent and vigorous condemnation from adversaries. The contention was that the application of the name of pleasure to this state was unjustified on the ground that two different things were thereby being denominated by one name. Cicero made a great to-do over this argument, but it is really superficial and captious. The fact that the name of pleasure was not customarily applied to the normal or static state did not alter the fact that the name ought to be applied to it; nor that reason justified the application; nor that human beings would be the happier for so reasoning and believing.