our official advice for sickness and diarrohea is 48 hours after the last bout of sickness or diarroahea.
As for your OH, he needs to keep an eye on his bloodsugars (they will probably be high) he also needs to check for ketones. If he has ketones, he needs to drink a lot of fluids every hour, he will need to give himself extra insulin, but I don't want to advise you of how much as that is a doctors job, and I wouldn't want to misadvise you. It will probably take him longer to recover than a person without diabetes.
Phone your diabetic team for more advice
(I have been diabetic since I was 10, and am now on the dafne regime, which means I can eat what I like and change my insulin accordingly, which is another reason I cannot advise you too completely on your OH's regime, as it may differ)