I don't have any great answers for you, but I don't see a good result in lowering the dose. You've held both 1.5 and 1.75 in the past for 2 1/2 days and not gotten good results. You've also held at 2, 2.25, and 2.5, and none of those brought good results. I don't care for the recent red #s and that certainly makes me go "hmmm" about raising the dose, but I don't see where lowering will get you anywhere. I mean you never know, maybe it's the answer, but based on your data so far I would make a 95% prediction you will see similar yellows & pinks - maybe a high blue, but nothing consistent. I'm happy to be wrong :mrgreen: but that's how it looks to me at the moment.
The only time I see a possible breakthrough is back on Lantus and 3.5u. So based on that my guess would be that he just flat out needs more insulin. If it were me, I think I would be raising in 0.2 increments every 3rd day or so (schedule permitting), and monitor fairly regularly for early big drops (so get in a spot test somewhere in the +2 to +4 zone most cycles).
It looked like on the 2.75 you might have gotten a breakthrough with the one good PS on 4/27. Without more data in that cycle it's hard to say for sure though if it was a U-curve or a downward curve, so it's hard to say if you continued with 2.75 if that would be the magic dose or not.
If you want to experiment with lower doses I think that is ok, but please do check for ketones regularly, and keep an eye on his symptoms. If he is acting like he is feeling worse, that could be a sign he needs more insulin. Of course there are hundred other possible reasons for feeling unwell.
Sorry it is not an easy road for you guys. Some cats just seem to be easier to figure out than others.