Max:
On the "interference" test: You've now said the rule isn't "always avoid pain," it's "avoid pain that interferes with enjoying katastematic pleasure." And that pain which doesn't interfere with katastematic pleasure because anticipation or recollection lets you manage it is fine to accept.
But what does "interfere" actually mean?
If "interferes" means displaces katastematic pleasure at that moment, since you agree that pleasure and pain are exhaustive and mutually exclusive — then I don't see that you are saying anything new. Every pain "interferes" with tranquility by definition, and that takes us back to giving up 17 units of pleasure to avoid 3 units of pain.
But if "interferes" means something like "disrupts" a settled state going forward, as a stomach ache from overeating does, then what you're describing is just prudence: weighing a pain against a pleasure with practical wisdom managing the accounting. That's not a rule that competes with "weigh total pleasure against total pain." That is weighing total pleasure against total pain, with prudence doing what Epicurus always said it does and it's the ordinary Epicurean calculus of pleasure and pain that anyone can understand.
So which is it? If it's the second, I don't think 'refer to tranquility' names a rule distinct from ordinary pleasure/pain calculus anymore — you've just brought back prudence in under a different name.
Now let's move to blessedness — I'll just say that I think your entire framework is wrong, and here is why. Epicurus' work must be taken as a whole and assembled logically without leaving out any of the key premises. Just like there are only bodies and space in the universe, there are only two feelings given by nature to decide what to choose and what to avoid. It is as inconceivable that we are going to end up with a goal other than the positive goal that nature gave us - pleasure - as it would be for anything in the universe to be supernatural, or consist of something other than bodies and space. But that's exactly what it appears to me the "Tranquility" argument does - it sets out a goal higher than and different from pleasure.
"Blessedness" or "Happiness" isn't a separate ingredient that only certain approved pleasures are allowed to contribute to. It's the character of a whole life, built from every pleasure in it — kinetic and katastematic together, held across memory, present experience, and anticipation. Nothing in the text requires sorting pleasures into a "counts" bin and a "doesn't count" bin before happiness can emerge from the mix. Friendship contributes to blessedness by being one of the richest sources of pleasure there is, whether that pleasure is 'active' (joy of company, conversation, shared meals, aid given and received) or 'stable' (confidence that comes from knowing help is there if you need it). There's no dilemma to resolve, because nothing forces friendship or any other active or stable pleasure to be only one or the other before it's allowed to count.
The dilemma only feels forced on you because it's built on the same premise you've already told me twice you can't ground in Epicurus — that a pleasure must be complete/perfect to confer blessedness. Based on that, you think the kinetic pleasures Epicurus talks so much about are structurally locked out from contributing to happiness. Drop that premise and the dilemma dissolves along with it.
Much of this goes back to the debate that others like Gosling & Taylor and Nikolsky have stated in much more detail. Your argument requires what I would say is unjustified emphasis of "stable" pleasures over the "active" pleasures that Epicurus indeed took note of, but for which his most devoted followers wrote and acted as if it was of no consequence, and for which there would be no real argument at all but for these passages such as PD3, PD18, PD20, and Menoeceus 128, which can all be given complete and consistent meaning without any such construction.
In my view this argument and many others are best settled by looking at the lives of the ancient Epicureans as they are recorded to have lived them. When I look at the life of Epicurus I see a man who devoted his life to campaigning as energetically as he could for what he saw was both the truth and a better way of life that rejects the claims of supernatural religion. He certainly knew that that path might well cost him a great deal of pain, and even his life, but he lived it anyway, and considered himself happy, even though the "tranquility" argument would have led him to take an entirely different course.
Your rule licenses risks taken to secure the tranquility of yourself or your friends already inside your circle. It doesn't explain why the Epicureans wrote and erected inscriptions and campaigned publicly, for strangers who owed them nothing and could offer them no security in return, against the most powerful religious and philosophical authorities of their day. That's not friendship-insurance. Those are choices made by men who had a clear idea of happiness that they thought was worth pursuing regardless of what it cost them.
Note: I posted this before seeing posts 84 and 85, but I'll comment on them as needed later.