I'm not in your position but metformin helps me walk too. When it works.
Like
@Freema said. Only a kidney expert can advise you about the safety of metformin, trialled and tested. To date.
My genes and sex hormones are currently protecting my kidneys.
So it's not inevitable that diabetes damages the kidneys.
Has other factors caused your organ problems or have you had decades of poorly controlled diabetes?
Metformin doesn't repair diabetes complications but definitely excellent for prevention.
I hope this helps.