How did the echo go? I'm glad you had it done. Neko's first echo only showed age related reasons for a murmur, so nothing bad. But it was a good baseline for later. Maybe you can get a sterile container from the vet and collect pee at home and take it in.
I was told that's low for acro cats in the acro cat open FB group
Don't listen to them. Especially not the person with the initials GC. Our experience here is that even following TR with acro cats is perfectly fine. Most of the acros here do follow TR unless they are eating dry food. Neko earned reductions when she went below 50 and was fine with it as I was monitoring closely. She was also very sensitive to carbs and I didn't need to give her much to boost her up. The only reduction exception is if a cat has been treated (cabergoline, SRT, etc.) in which case we raise the reduction point to 70. Malcolm is not in that category yet. 90 on a pet meter is perfectly safe.
Malcolm is also seeing a lot of numbers over the renal threshold, which varies by cat but is typically in the 200's (pet meter) and above. More insulin will lower those high numbers. Acromegaly is hard on the kidneys, you want to try to get him to a safe dose where he's spending time below the renal threshold, so nadirs in the 90-149 range since you are following SLGS.
Acro cats with diabetes are diabetic cats. They have diabetes type 3 - from other causes, some refer to this type as HS (hypersomatotropism) associated DM or diabetes mellitus. HS is the name of the pituitary tumour, acromegaly is more properly the symptoms associated with the tumour. To say acrocats are not diabetic is hogwash. If I had the time, I could dig and find the several articles I've seen by researchers in acromegaly who describe them as diabetic. For now, here is just one of them: see the story of Case 2:
(2020) Updates in Feline Diabetes Mellitus and Hypersomatrotropism
Note, not all cats with hypersomatotropism (the pituitary tumour) have diabetes, as that is a late stage symptom. But once they need insulin, they are diabetics and have acromegaly.