You and him could both meet a diabetes practitioner - explaining to him how dangerous alcohol can be to the system when you're a Type 1 diabetic. You could repeatedly call him and request him to place alarms on his phone - then physically record the sugar levels. Even if he agrees to message you his sugar levels from time to time, that would most likely to lower your stress.
Once again, just try talking to him - if you feel that in a conversation you are unable to fully convey your arguments/points to convince him, try other methods. You could write it down on a piece of paper and give it to him or you can get emotional and literally tear up in front of him - any measure to properly get you fear across.
Good Luck