I think what I’m struggling with is that to me, absence of pain sounds like a state in which I’m perfectly content and don’t feel like I need anything more. At the same time, my practical evaluation of Epicurean ethics is that of prudence and hedonic calculus. In my head, these two ideas don’t quite seem to align. It doesn’t feel so clear.
And I think it sounds that way to most people, and that's why Cicero and Plutarch use it like a sledgehammer against Epicurus, because understanding it as "being satisfied with the bare minimum of life" is deadly and no healthy person in their right might is going to accept that. (Of course there are many people who are not healthy or in their right mind who *do* accept that version, and that just makes the problem worse.)
All of these issues are very much a test like "the size of the sun is as it appears to be." If you are satisfied then of course you don't want any more -- that's the definition of being satisfied. The real question is knowing the difference between "when" you should be satisified, and when you shouldn't.
All of us have this baggage from being raised Christian (or religious in some way) with a mixture of Buddhism and Stoicism thrown in to emphasize that wanting pleasure or anything more than you currently have is a character flaw. That's as much the problem as anything else. If you were born on a desert island with nothing but nature teaching you through observation of how all other life lives, you'd never have a moment for thinking that you shouldn't sing, dance, fly, embrace, etc, just like all the other animals do when they satisfy their thirst and hunger.
But Epicurean philosophy can be twisted into justifying just such an outcome, and in that respect the result is worse than Stoicism or religion - at least those (or most of them) promise a life in heaven as a reward for asceticism now. The "Absence of Pain" Epicureans don't even get that -- they get asceticism for the sake of whatever it brings in this life, which is nothing.
As humans we live through using our minds properly, and Epicurus is pointing the way to proper thinking. Plato et al are wrong to say that life is neutral or suffering with a few intervals of pleasure. The right attitude is that life is enjoyable and needs to be enjoyed, and so we set our minds to enjoying every aspect of it that can possibly be enjoyed in mind and body, and that can include anything and everything that isn't explicitly painful.
I'd say the most helpful way of looking at things is to focus on how short life is, and how when it's over it's over. If you really focus on what that means, what kind of a human being are you if you don't want to use your time the very best way possible? If "pleasure" is everything that is desirable and "pain" is what is undesirable, then the right philosophic attitude is to pursue as much "pleasure" as possible.
All of these words have specific meanings that can be extremely helpful, or if misunderstood, extremely harmful. But this is the importance of philosophy. No one said this was easy - if it was easy there'd be hundreds of Epicuruses instead of essentially only one.
Looking back over your questions I'll go back to the best example I know of. You only have some much time in life to experience what you're going to experience. It is helpful to visualize your total lifetime as a jar, which you must decide how to use. The jar by definitional choice can contain only (1) pleasure or (2) pain. No part of it is ever empty. The palns and pleasures it can contain are all possible mental and bodily pleasures.
It's up to you to decide whether to act to control what will be in that jar. If you identify pleasure widely and understand that it's not just mental and physical stimulation but all kinds of mental and physical health, then it becomes possible for most everyone to see that it is a practical goal to work toward filling that jar with pleasures. If you DON"T view pleasure that way, then it will seem like and be a fruitless task to fill the jar with pleasure, and you'll never find a way to do it no matter how hard you chase stimulation.
That's the paradigm everyone is faced with, but they don't have to accept it. They can choose to drift through life and take no concern for what is in their jar, and as a result they will never be satisfied and their time will be spent on things that end up being more painful than pleasurable.
So in general I'd say that this is the big picture. Once you've got the big picture it's up to you to apply it - simply reading it or acknowledging that it exists doesn't accomplish anything. Time is always ticking, and the time that passes without working to maximize pleasure never comes back.
To me this isn't dark or discouraging, it's highly motivational, and it doesn't encourage me to spend all my time looking back and "feeling satisfied," it leads to a proper balance of appreciating past, present, and future, and acting appropriately toward them all.