I guess we maybe need to consider a different insulin
I think maybe a different approach should be tried first.
PMPS 461 1/2 can 15% carb fed
+1 401 no food
+1.5 346 fed 1 tsp. 15%
+2 302 no food
+2.5 220 fed tsp 1.9%
+3 175 fed tsp. 6.1%
+3.5 133 fed 1 tsp. 15%
+4 133 fed 1 tsp. 9.2%
+4.5 88 (131 on human meter) fed 1 tsp. 22% (lick e lix)
+5 119, (133 on human meter) fed 1 tsp. 15%
+5.5 113 (151 on human meter) fed 1 tsp 2.9%
+6 182 no food
+6.5 169 (211 human meter)
I would not have fed high carb food as often as you have been, nor should you need to continue to test or look at his BG every half hour until +6.5. That is unsustainable. Before people had Libres (very recent technology), it was a lot less tests/ear pricks. Rather, you need to learn how Merlin responds to Lantus, and test appropriately. Learning his onset, nadir, and duration will make your life much easier. Then you'll know when to test and learn when to feed. By the way, food experiments take time, you can't switch it up every day.
First, I'd like to figure out when his onset is, then you can feed some higher carb food about 20-30 minutes before then to slow his fast drop. Feeding HC at preshot doesn't make sense to me as it's too early in the cycle, he's not dropping then. It also hides when his onset is as his numbers are artificially inflated by carbs.
Next step is figuring out his nadir, cause the cat is on his way up after that, and you are closer to bed. I would not have fed HC at that 88 at +4.5. 88 is a very safe number. I would have given LC and tested 1/2 hour later. If he'd been flat or starting to rise at that point, you'd be much closer to going to bed. However by giving HC, you have to wait a couple hours after that HC wears off to see if he's still safe. I definitely would not have fed anything higher carb at +5. He was on his way up and over 100. That also delayed you getting to bed sooner. And probably shortened duration.
I had a late nadir girl, I was very focused on learning what I could do to go to bed earlier. Merlin looks like a early nadir cat, that should make life much earlier for you in the long run, once you learn the onset, nadir and his response to food.
I would like to get someone who had a cat that dived early, to take a look at Merlin's situation. However, I'll be frank, any daily thread over 200 posts is intimidating to read and digest. The summaries Suzanne have been doing help, but there still is a lot to wade through. Figuring out when to test so you don't have to get data every half hour will help shorten the content.