Your grandad was following advice given before the 1980s when typically using only long lasting insulin (which was all that was available) and strict routines were the only way to survive and be healthy with T1D. You should read that DCCT citation I link in my post, it is a good read, about the impact of following the treatments of nearly 1,500 diabetics and their long term complications. DCCT lead to a lower HbA1c being the goal as it is the largest predictor of long term issues. There are many books like “think like a pancreas” and “sugar surfing” which explain and use the same methods I explain in the post. If you are interested. Also, I would love to meet a person who can write a multi page blog post in a panic. Like “help my car is on fire: a history of car fires”