You are raising some excellent points -- these are the issues that need discussing.
First, as to singular or plural in PD03, it looks to me like the translators are all over the board on which is corrrect. Given their disagreement it would be good to hear what Don or Bryan think, because I agree with your perspective that it would make a difference to us in English whether it is singular or plural. But given the different variations I expect that's not going to be easy to sort out.
Among the most important parts of your post was this part
I think this focus allows me to not worry about which pleasure, or how much of it will make me happy more often than sad when navigating the reality of every day life. This focus tells me to first notice what is painful bodily and/or mentally and address the removal of that condition. When I do that I'm left with the various stages of pleasure and happiness however I define it.
I think that depending on how one interprets what you have written there you are going to find huge differences of opinion.
If what you mean is that your first priority is to seek out and eliminate any bodily or mental pain from your life before you turn to any pleasure, and that in the process of eliminating those pains it makes no difference what pleasures you choose to employ, then that's quite a stark statement.
If what I gather to be Kelly Arenson's opinion is correct - that katastematic pleasure is that kind which we experience in smelling roses or listen to music which is not required of us because we experience a lack of rose-smells or music, then arguably someone who used your formula would never pursue roses or music until they reach a state of perfect painlessness.
Clearly there is a dual focus that arises from the existence of both pleasure and pain. We want to BOTH choose pleasure and avoid pain. The question is whether it is correct to erect the elimination of any pain of body or mind as the "prime directive" that is to be pursued before one would choose to pursue any pleasure of any type or degree, especially a type of pleasure that is "discretionary" because it is not something we need for the relief of a specific pain.
I suspect you will say that that is not what your formulation is doing, but my personal opinion is that it comes very close to saying that, and I would not agree that that would be the correct conclusion. Sometimes we choose pain in order to avoid a worse pain or achieve a greater pleasure.
These are exactly the issues that are both the subject of this thread and of the thread on Kelly Arenson's book, so I'll just note here that people reading into this should refer to both threads.
