So regarding the Siuan/Leanne situation. Are you actually proposing that Leane was referring to the numerical strength level she is now at, rather than to the amount of Power she can now channel?
In other words, when she says she is less than half as "strong" as she was before, are you trying to suggest she was not referring to absolute strength, but instead to her numerical position on a scale which only includes Aes Sedai?
It is important that you clarify this, because if this is seriously your contention then it is a position that is easily refuted. But first I want to clarify if that is indeed your argument.
Not the actual numbers of these levels. I don't think the Aes Sedai have actual numbers for these levels, but they are the people most acutely aware of them.
Now, I'm not saying the sentence cannot be read the way you read it. I'm saying, however, that since extra-textual sources (RJ's notes) are very clear the levels have a linear progression, and that therefore there is no way for Siuan (or Leane as the case is here) to lose a third of their strength in terms of bulk quantities of the Power they could use.
What we then have to do is either treat it as a mistake or interpret it with in line with the superseding information from the guide.
This seems to have always been the tension here. You have always chosen to ignore the supremacy of RJ's own statements and only use your interpretation of the text. I let my interpretation be swayed by what the author says.