Nice summary, Godfrey . I would agree with all of your points.
And I also agree that getting the distinction between desires and pleasure clear in one's mind is crucial. I particularly like your point about desires being potentially limitless while pleasure/pain each have a natural limit (the elimination of the other feeling: No pain = all pleasure simply because if one is filled **with** pleasure, there's no room for pain. It's the *filling up with pleasure* that's important, not the "removing pain.")
On the desire side, one can continue to lust for power no matter how much power you already have. You can desire more money, no matter how much money you already have. There is no natural limit to those kinds of desires. In one sense, that's why they're empty/void, *nothing* can fill them up!