It does sounds hopeful but I always think of these times as being cautiously optimistic.
When they are in jail they have much time to think. Promises are made of how things will be different.
The real world doesn't care much about their recovery. Well maybe the codependents do! LOL!!!
If they don't find support and coping skills the same issues are bound to come up.....which put them in the place that they promised they wouldn't be in again.
I wouldn't push or suggest or give advice anymore. He knows you are supportive.
As for the ending of the letter with a request....I suppose that may be prison or even the person writing IDK. I do know that if you feel uncomfortable with the requests say so. You don't have to walk on eggshells with him.