This is NOT a dosing advice, as I am inexperienced with ProZinc (we are on Lantus) just an observation, which I'm sure a lot of, more experienced members will perhaps disagree with:
Seeing how her PMPSes are often in the same range, and her AMPSes are low/often the lowest - could it be that she'd benefit from a QD dosing instead of a BID?
I understand the mechanics of insulin absorption/metabolism, thus why the BID distribution works best for most cats (emphasis is on most). However, I heard it from other owners as well as from vets when talking about the use of ProZinc in particular, that sometimes a once-a-day administration of it is enough, because after all, it all comes down to the individual cat's metabolism.
I wonder what pattern would she have shown keeping her at 3.5 IU QD. Whether she would have stayed yellow both PMPSes, in blues throughout each side of a 24hr cycle, that would gradually turn into greens closer to "nadir" which perhaps falls on the 12th hour aka AMPS. Something like this:
PMPS +1 +2 [...] +11 AMPS +1 +2 [...] +11 PMPS
beginning of cycle ---- nadir ---- end of 24hr cycle
I understand she dropped low on that 4 IU in the PM cycle a few days ago, however, I noticed on my cat, that after a delay and/or even the slightest dose increase, his body would panic and his BG would hit nadir sometimes as shockingly early as +2/+3 of the cycle, as opposed to his usual +5/+6/+7. (Hence why the protocols are written the way they are, because their little bodies need time to adjust to a certain dose, to see its full, evenly distributed potential. It is not to say that 4 IU was a good dose. It was definitely too high for her, and the reduction was earned. It is to point out a reoccurring pattern I observed on my own cat, that may be relevant to yours, too.)
So if my theory of a 24hr cycle for Angel would be applicable, and if my math is mathing correctly, that +2/+3 nadir "shock drop" after delay/increase would fall right to those times where Angel went low at +7/+8.
Does it make any sense?
Again, these are just my observations and the inputs I have encountered from vets and other ProZinc users. I may be completely wrong, and I'd urge you to perhaps discuss this with more experienced members and/or your vet. I just wanted to share my thoughts after looking at your spreadsheet, because I know from experience that we can get very accustomed seeing our own sheets day in and day out, that we may overlook certain patterns that perhaps stand out to others.