With respect, your friend with 40 years of diabetes may be out of date.
I am guessing (I may be wrong) but is he Type 1? This can lead to a very different view of diabetes.
Again his view may be correct; we are learning all the time.
Which reminds me, I've just caught up with my 84 year old Uncle who has been T2 for 20 years. Almost from the outset he has been on Metformin and Gliclazide and his annual HbA1c is still around 7.0. I am very impressed. I am only 10 years in but there seems to be some hope in my genetic line for long term diabetes management.
It is your body and your life, but always be wary of picking one voice from the crowd because it says what you want to hear. Then again, we all have our personal views so take your pick.
The good news is that there is plenty of time to try different things, and to learn new things.
More Metformin and plenty of exercise may work for you.
If you are relying on Metformin and exercise you should take a very hard look at your diet because you need to give your body all the help it can get.
You (most of us) are allergic to carbohydrates.
Diabetes is generally the inability of your body to process carbohydrates correctly.
So limiting the amount of carbohydrates can help your blood glucose control.
Final note, and wishing you well. Your blood glucose levels that you have reported to us on 1,000Mg of Metformin are still dangerously high. You need to be getting 140 or below before you are on the path to decent long term control. If you do not achieve this on Metformin and exercise, and you wish to follow your friend's advice, then you need to talk to your Doctor about starting on insulin.