Just for some background, my recollection is he was all about the high #s til you hit a breakthrough a few weeks ago - since then he's been in this pattern of screaming down to green nadirs and then right back up to high #s much of the time. It looks like when you lower the dose a little though then you just get a higher next PS rather than the other way around, so that looks like lack of duration, though of course when you are in a rebound pattern that complicates the picture - even if you don't cause rebound in a specific cycle, you can still have carry over high #s from earlier cycles.
It's a dilemma. I agree insulin resistance isn't your issue - I don't think with that you hit green nadirs. Could be he had that before you were getting the good nadirs though, but you've certainly broken through it.
I would think some more experimenting with a slightly lower dose might be in order, but I wouldn't want to see him just sit in higher #s again. In theory when you reduce the dose and rebound clears the #s should come down some on their own - my recollection is you haven't seen that when you've tried, but could be a matter of honing in on the correct dose to try, or giving it the right amount of time. Sometimes it can take a couple days to clear.
My sense ultimately is you may want to try a different insulin. Alternately I think early shooting is an option, but IMO too stressful to contemplate unless you are really gung ho about it. On the plus side though, maybe he has been spending enough time in good #s that liver training is less of an issue any longer, so maybe with a slightly lowered dose you would see better #s now? I'm not sure though, b/c whenever you lower it for the evening dose now, the morning PS is super high, vs. the higher dose in the AM is giving you much better PSs in the PM.
Well, hmmm, not much help there, just musing...