I wouldn't worry too much about dissecting every # and every cycle. The reality IMO is that it isn't a clear-cut illness and the #s are just a guideline more than anything else. I don't think it is essential to know exactly why some cycles are wonkier than others, or for all of us here to get consensus on what is going on. Of course those things would be nice... but... not gonna happen IMO.
Bud is getting quite a lot of good #s, I would focus on that, and focus on where you want to go from here. If you want to shoot 12/12, I would pick the time that you want to use and go ahead and switch to that. If you want to ensure a shootable # at every +12 I think you will need to shoot a slighly lower dose (than 0.75) to achieve that.
I would also tend to focus on what you KNOW, rather than driving yourself crazy trying to figure out what you don't know. Most if not all of us have been in your shoes, and take it from me, you don't want to tear out all your hair like we did. Save a little for old age. :lol: My experience with FD is you will never have all the answers, and if you are getting pretty decent #s and your cat is doing reasonably well, then ... woohoo!!!!
I don't see any major mysteries here, in the sense that I think you have pretty decent #s and you have a fairly clear-cut range of doses that appear to be too low (0.2) and doses that are likely too high (anything over 0.75). I would continue with doses between those two ranges. I don't see any need personally to over-debate the 0.75u question. If you are comfortable with the results you are getting, then stick with that dose. If you would like to try something a hair lower like some of us have suggested, you try that and see what data you get. You may get results that are more in line with what you want for 12/12 and that are easier to work with, or you may find that you actually need the 0.75 to get good #s.
Bottom line IMO is that much of FD is about data collection and trial & error. You try something, get data, and then evaluate your next move. I don't think any of us can say beyond a shadow of a doubt what is going on. But if you try different things and get data, that is what will make it clear. If you try 0.6 or so and don't get good #s, well then we know she really does need more than that. If you try that and get pretty U-curves that are more in 12/12 pattern and perfect 150 PSs every cycle, then we know a slightly lower dose works better for her, at least from a 12/12 perspective. Won't know for sure til you try it.
I know it is frustrating not to have clear answers and explanations, but personally I don't think our debating the #s is going to give you an answer. Even if we all reached consensus, we could still be wrong. Interpretations are just interpretations.