From your original post it sounded like when he went on treatment as well as the GI symptoms from metformin he had low blood sugars which can make you feel terrible.
I guess the endocrinologist has proven the diabetes but in my day the initial treatment was as
@tgh said -diet + exercise. here is 1 study (there are many) suggesting diet + exercise is the best treatment initially for type 2 diabetes.
As for low blood sugars above 3.9 is not considered a low blood sugar. Keep something on hand to take if you are often having low blood sugars.
Personal story. 15 years ago my random blood sugar was 16.5 Hba1c was 6.5. Initially diet only. With exercise in the last 3 years sugar levels in normal range and Hba1c ~5,2. My haemochromatosis makes me more likely to be diabetic.