Good points.
It's the regular equation of freedom from pain as "not only" the same thing as "pleasure" but relating it to "the most intense pleasure possible" that I think causes the most potential for confusion.
QuoteCicero: "...[B]ut unless you are extraordinarily obstinate you are bound to admit that 'freedom from pain' does not mean the same thing as 'pleasure.'" Torquatus: "Well but on this point you will find me obstinate, for it is as true as any proposition can be." ... Cicero: Still, granting that there is nothing better (that point I waive for the moment), surely it does not therefore follow that what I may call the negation of pain is the same thing as pleasure?" Torquatus: "Absolutely the same, indeed the negation of pain is a very intense pleasure, the most intense pleasure possible." CIcero - "On Ends" Book 2:iii:9 and 2:iii:11 (Rackham)
I don't see this as something that Cicero has manufactured to be confusing, and I see it has inherent in a superficial reading of the Letter to Menoeceus, which is why I am fixated upon it.
If we were to say "By pleasure we mean the absence of pain" then a strictly literal reading of that sentence leads to "you can't have pleasure until pain is totally absent" and that leads to the creation of "absence of pain" as some kind of highly unusual state that is divorced from standard reality.
Seems to me that potential ambiguity in the presentation is what Cicero is picking up and running with for all he is worth.
I think it's reconcilable and explainable, but takes effort beyond just reading that passage from Menoeceus over and over.
In English "pleasure" can go up and down in intensity, duration, location (at least).
To say that "absence of pain" is "the same as" pleasure" would imply that it too can go up and down.
But to then state that "absence of pain" is "the highest" or "most intense" pleasure indicates that it is at a fixed position (at least to my way of reading).
It's not really any unusual use of the terminology by you Don that is causing me to think this can be made more clear, but dividing up what are two apparently separate things (varying pleasure) and (pleasure at the highest notch) that I think needs to be made more clear.
I am presuming that the Epicureans saw this as one issue -- pleasure can vary, and can only go so high, but the same thing is being measured all the way up and down the scale.
Uses of these terms "ataraxia," "aponia," "highest good" etc would seem to imply that there is something different at that top notch location.
I do NOT think Epicurus saw anything uniquely different about the top notch vs the lower readings (especially for example 99.9%) but using the terms loosely can be read to imply to casual readers that you don't have anything unless you're at 100%.
It's that issue -- that you want the highest but will take what you can get - that I sense needs to be made more clear in order for the terminology and the system to be made as clear as possible.