There are some folks with Type 1 posting on the Dr. Bernstein message board who are enthusiastic about benfotiamine.
Some people there also recommend a form of Alpha Lipoic Acid a supplement which, if I recall correctly, Dr. Bernstein states can increase insulin sensitivity in a Type 1. He recommends taking it with Evening Primrose Oil. There is one version of ALA that is supposedly more potent, but I can’t recall what it is.
Is it possible that with advancing age you are becoming more insulin resistant? If that is possible, could metformin perhaps make your insulin work better? I’m insulin sensitive, but when I take metformin I get much smoother blood sugars. The difference is between 4.5 units without Met and 3.5 units with to cover roughly 40 grams with, but the met stops the liver from dumping glucose at meal time and that really makes the blood sugars after meals a lot better.
I know this isn’t a treatment usually given Type 1s, but everyone gets more Insulin Resistant as they age, even normal people, so it might be something to thing about. Metformin is the longest tested, safest, diabetic drug.