Being "without pain" (completely, entirely) is the maximum limit of pleasure. It is not a state that the average person frequently, or maybe ever, enjoys. I think it is a mistake to use this or similar expressions casually for a general audience unless the meaning is very clear.
I agree and think you are exactly right. This is a huge point and requires that we emphasize it. I don't think that Epicurus would used wording that implied this possibility if he were not writing (to Menoeceus) to someone he expected to know better than make this mistake.
As to Torquatus, I would not put it beyond Cicero as a lawyer to put these words in Torquatus' mouth exactly for the purpose of creating this confusion. DeWitt pretty much says exactly that with his comment that Cicero could not have misrepresented Epicurus so effectively had he not understood Epicurus so well.
Now 2000 years later we are having to live with the hand we are dealt. The potential confusion that Cicero exploited has become the actual orthodoxy in the mind of most everyone who thinks they understand Epicurus.
I doubt there is any way to address the problem rather than head-on. Pick up where Cicero amplified the distortion through selective wording, then point out that Menoeceus would have known better than to fall for it, because he knew the teachings as a whole. Then go back straight into the physics and to the Platonic anti-pleasure no-limit argument to explain where the binary argument comes from in the first place.
And I think also this leads us straight back into the knowledge issues being discussed in Academic Questions. This problem of confusing abstractions is why Epicurus was insisting on always checking everything by the sensations, anticipations, and feelings, and never falling into absolute abstractions that don't reflect the actual situation at a particular time and place.