His wanting to go inpatient may be yet another desire for someone 'else' to fix things, more magical thinking that he doesn't have to take care of himself.

It's important that he learn to do this as soon as possible, for his mental health and his diabetes management. I'm really glad that you stood up for yourself! It is a big step, and an intimidating step he's taking. Good for both of you!

Maybe there is a day program available through the hospital.