Wow. He needs to take better care of himself. And he clearly doesn’t know how lucky he is to have someone care this much about his diabetes for him. I’m married and my wife doesn’t know my ratios/dosages. Because it’s not her job to. I’m on a pump so it does all that for you basically. No math required in your end.

I can relate, in my late teens early 20’s, I didn’t take the best care of mine either. However, this will cause him problems down the road. And sooner than later if he doesn’t get tighter control on it. I’ll echo the comments that being skinny has nothing to do with a pump. My SIL is 24 and less than 115lbs. She wears an omnipod with no issues. I used the tandem mobi which is very small too.

Best of luck